For the time being the DateTime object can be set to the AxisCrossingPoint on the client. For example:

ASPX:

		<script>
			function OnLoadHandler(sender, args) {
				var kendoChart = sender.get_kendoWidget();
				var opts = kendoChart.options;
				opts.categoryAxis.axisCrossingValues = [0, new Date("2014, 11, 05, 19:15:00")];
				kendoChart.setOptions(opts);
			}
		</script>
		<telerik:RadHtmlChart runat="server" ID="RadHtmlChart1" Width="600px" Height="400px">
			<ClientEvents OnLoad="OnLoadHandler" />
			<PlotArea>
				<Series>
					<telerik:LineSeries Name="Product 1" DataFieldY="SellQuantity">
					</telerik:LineSeries>
				</Series>
				<XAxis DataLabelsField="SellDate" BaseUnit="Minutes">
					<LabelsAppearance Step="15"></LabelsAppearance>
					<MinorGridLines Visible="false" />
					<AxisCrossingPoints>
						<telerik:AxisCrossingPoint Value="10" />
					</AxisCrossingPoints>
				</XAxis>
				<AdditionalYAxes>
					<telerik:AxisY></telerik:AxisY>
				</AdditionalYAxes>
			</PlotArea>
			<ChartTitle Text="LineSeries"></ChartTitle>
		</telerik:RadHtmlChart>


C#:
	protected void Page_Load(object sender, EventArgs e)
	{
		if (!Page.IsPostBack)
		{
			RadHtmlChart1.DataSource = GetData();
			RadHtmlChart1.DataBind();
		}
	}

	protected DataTable GetData()
	{
		DataTable dt = new DataTable();

		dt.Columns.Add("ID", typeof(int));
		dt.Columns.Add("SellQuantity", typeof(int));
		dt.Columns.Add("SellDate", typeof(DateTime));

		dt.Rows.Add(1, 2, new DateTime(2014, 11, 05, 18, 22, 22));
		dt.Rows.Add(2, 5, new DateTime(2014, 11, 05, 18, 56, 22));
		dt.Rows.Add(3, 6, new DateTime(2014, 11, 05, 19, 14, 22));
		dt.Rows.Add(4, 4, new DateTime(2014, 11, 05, 19, 48, 22));
		dt.Rows.Add(5, 7, new DateTime(2014, 11, 05, 20, 12, 22));

		return dt;
	}

When using custom shapes (circles, triangles, etc) in a RadHtmlChart, the custom shape should be displayed in the legend instead of always a square.  This is because when printing with a black & white printer, the colored squares won't help the reader read the chart, however the shapes would.

Currently the available appearance options of the line in Area, Line and ScatterLine Series are width and background color. Expose additional option for changing the dash type(e.g. dash, dashDot, Dot, etc). For the time being the following workaround can be used:
		<script>
			function pageLoad() {
				var chart = $find("<%=RadHtmlChart1.ClientID%>");
				//DashType: dash, dashDot, dot, longDash, longDashDot, longDashDotDot, solid
				chart._chartObject.options.series[0].dashType = "dot";
				chart.repaint();
			}
		</script>
		<telerik:RadHtmlChart ID="RadHtmlChart1" runat="server" Width="600px" Height="400px">
			<PlotArea>
				<Series>
					<telerik:LineSeries Name="Series 1">
						<SeriesItems>
							<telerik:CategorySeriesItem Y="30" />
							<telerik:CategorySeriesItem Y="10" />
							<telerik:CategorySeriesItem Y="20" />
						</SeriesItems>
					</telerik:LineSeries>
				</Series>
				<XAxis>
					<Items>
						<telerik:AxisItem LabelText="item 1" />
						<telerik:AxisItem LabelText="item 2" />
						<telerik:AxisItem LabelText="item 3" />
					</Items>
				</XAxis>
			</PlotArea>
		</telerik:RadHtmlChart>

Currenlty Series like Bubble, Bar, Column, Donut, Pie and Candlestick do not expose any appearance properties for the Series border. Expose appearance border properties like width, dashtype, color and opacity.

Temporary workaround for managing the border appearance:
Javascript:
	<script language="javascript">
		function pageLoad() {
			var chart = $find("RadHtmlChart1");
			chart._chartObject.options.series[0].border = {
				width: 2,
				color: "black",
				dashType: "dash",
				opacity: 0.2
			}
			chart.repaint();
		}
	</script>

ASPX:
	<telerik:RadHtmlChart ID="RadHtmlChart1" runat="server" Width="600" Height="400">
		<PlotArea>
			<Series>
				<telerik:ColumnSeries>
					<SeriesItems>
						<telerik:CategorySeriesItem Y="30" />
						<telerik:CategorySeriesItem Y="10" />
						<telerik:CategorySeriesItem Y="20" />
					</SeriesItems>
				</telerik:ColumnSeries>
			</Series>
		</PlotArea>
	</telerik:RadHtmlChart>

The feature will be similar to Plot Bands (see http://demos.telerik.com/aspnet-ajax/htmlchart/examples/functionality/plot-bands/defaultcs.aspx demo), however, the width of lines will not be dependent on the y-axis scale.

For the time being the property can be set through the underlying Kendo Chart widget. For example:

		<script>
			function OnLoad(chart) {
				var widget = chart.get_kendoWidget();
				//also applies for the minor grid lines - replace majorGridLines with minorGridLines
				//Numeric series
				widget.options.xAxis.majorGridLines.step = 5;
				widget.options.yAxis.majorGridLines.step = 5;
				//Category series
				//widget.options.categoryAxis.majorGridLines.step = 5;
				//widget.options.valueAxis.majorGridLines.step = 5;
				widget.redraw();
			}
		</script>
		<telerik:RadHtmlChart runat="server" ID="BubbleChart" Width="500" Height="400">
			<ClientEvents OnLoad="OnLoad" />
			<ChartTitle Text="Market Share Study">
			</ChartTitle>
			<PlotArea>
				<Appearance>
					<FillStyle BackgroundColor="White"></FillStyle>
				</Appearance>
				<XAxis MinValue="0" MaxValue="100" Step="10">
					<MinorGridLines Visible="false" />
				</XAxis>
				<YAxis MinValue="0" MaxValue="100" Step="10">
					<MinorGridLines Visible="false" />
				</YAxis>
				<Series>
					<telerik:BubbleSeries>
						<Appearance FillStyle-BackgroundColor="#6ab2c9">
						</Appearance>
						<TooltipsAppearance DataFormatString="Percentage of Market Share: {2}%<br /> Number of products: {0}<br /> Sales: ${1}" />
						<SeriesItems>
							<telerik:BubbleSeriesItem Size="3" X="5" Y="55" />
							<telerik:BubbleSeriesItem Size="12" X="14" Y="80" />
							<telerik:BubbleSeriesItem Size="33" X="20" Y="60" />
							<telerik:BubbleSeriesItem Size="10" X="18" Y="24" />
							<telerik:BubbleSeriesItem Size="42" X="22" Y="32" />
						</SeriesItems>
					</telerik:BubbleSeries>
				</Series>
			</PlotArea>
			<Legend>
				<Appearance Position="Right"></Appearance>
			</Legend>
		</telerik:RadHtmlChart>

The feature should be like the one in KendoUI' https://docs.telerik.com/kendo-ui/api/javascript/dataviz/ui/chart#configuration-series.aggregate
For the time being it can be set through the chartObject:
ASPX:
		<telerik:RadScriptManager ID="RadScriptManager1" runat="server"></telerik:RadScriptManager>
		<script type="text/ecmascript">
			function pageLoad() {
				var chart = $find("<%=RadHtmlChart1.ClientID%>");
				chart._chartObject.options.series[0].aggregate = "sum";
				chart.repaint();
			}
		</script>
		<telerik:RadHtmlChart runat="server" ID="RadHtmlChart1" Width="640px" Height="480px">
			<PlotArea>
				<Series>
					<telerik:LineSeries DataFieldY="SellQuantity">
					</telerik:LineSeries>
				</Series>
				<XAxis BaseUnit="months" DataLabelsField="SellDate">
					<LabelsAppearance DataFormatString="d">
					</LabelsAppearance>
				</XAxis>
			</PlotArea>
		</telerik:RadHtmlChart>
C#:
        using System.Data;
	protected void Page_Load(object sender, EventArgs e)
	{
		RadHtmlChart1.DataSource = GetData();
		RadHtmlChart1.DataBind();
	}

	protected DataTable GetData()
	{
		DataTable dt = new DataTable();

		dt.Columns.Add("ID", typeof(int));
		dt.Columns.Add("SellQuantity", typeof(int));
		dt.Columns.Add("SellDate", typeof(DateTime));

		dt.Rows.Add(1, 2, new DateTime(2012, 06, 12));
		dt.Rows.Add(2, 5, new DateTime(2012, 06, 13));
		dt.Rows.Add(3, 6, new DateTime(2012, 06, 17));
		dt.Rows.Add(4, 4, new DateTime(2012, 07, 18));
		dt.Rows.Add(5, 7, new DateTime(2012, 07, 20));

		return dt;
	}

The functionality is similar to the one in Kendo UI Chart (http://demos.telerik.com/kendo-ui/dataviz/line-charts/notes.html) :
http://dojo.telerik.com/OZuNU

For the time being you can try to utilize the kendo.drawing API in order to place the text on a particular position.  This forum may be helpful on the matter - http://www.telerik.com/forums/custom-drawing#sOkmYWbfrUW404Rr13eLDQ

For the time being you can use the following workaround:
		<script>
			function OnLoad(sender, args) {
				var kendoWidget = $find('<%=RadHtmlChart1.ClientID%>').get_kendoWidget();
				kendoWidget.options.legend.reverse = true;
				kendoWidget.redraw();
			}
		</script>
		<telerik:RadHtmlChart ID="RadHtmlChart1" runat="server" Width="600" Height="400">
			<ClientEvents OnLoad="OnLoad" />
			<PlotArea>
				<Series>
					<telerik:ColumnSeries Name="Series 1">
						<SeriesItems>
							<telerik:CategorySeriesItem Y="30" />
							<telerik:CategorySeriesItem Y="10" />
							<telerik:CategorySeriesItem Y="20" />
						</SeriesItems>
					</telerik:ColumnSeries>
					<telerik:ColumnSeries Name="Series 2">
						<SeriesItems>
							<telerik:CategorySeriesItem Y="2" />
							<telerik:CategorySeriesItem Y="5" />
							<telerik:CategorySeriesItem Y="7" />
						</SeriesItems>
					</telerik:ColumnSeries>
					<telerik:ColumnSeries Name="Series 3">
						<SeriesItems>
							<telerik:CategorySeriesItem Y="9" />
							<telerik:CategorySeriesItem Y="11" />
							<telerik:CategorySeriesItem Y="13" />
						</SeriesItems>
					</telerik:ColumnSeries>
				</Series>
				<XAxis>
					<LabelsAppearance RotationAngle="33"></LabelsAppearance>
					<Items>
						<telerik:AxisItem LabelText="Item 1" />
						<telerik:AxisItem LabelText="Item 2" />
						<telerik:AxisItem LabelText="Item 3" />
					</Items>
				</XAxis>
			</PlotArea>
		</telerik:RadHtmlChart>

A functionality similar to KendoUI's error bars - http://demos.telerik.com/kendo-ui/dataviz/line-charts/error-bars.html

For the time being the following workaround can be used:

JavaScript:

    <script>
        function pageLoad() {
            var chart = $find("<%=RadHtmlChart1.ClientID%>");
            chart._chartObject.options.series[0].labels.background = "yellow";
            chart._chartObject.options.series[0].labels.border = {
                width: 2,
                dashType: "dashDot",
                color: "green"
            };
            chart.repaint();
        }
    </script>

ASPX:

        <telerik:RadHtmlChart ID="RadHtmlChart1" runat="server" Width="600" Height="400">
            <PlotArea>
                <Series>
                    <telerik:ColumnSeries>
                        <SeriesItems>
                            <telerik:CategorySeriesItem Y="10" />
                            <telerik:CategorySeriesItem Y="30" />
                            <telerik:CategorySeriesItem Y="20" />
                            <telerik:CategorySeriesItem Y="25" />
                        </SeriesItems>
                    </telerik:ColumnSeries>
                </Series>
            </PlotArea>
        </telerik:RadHtmlChart>

A nice improvement in RadHtmlChart will be the ability to control the speed of chart's transitions.

Currently the default pivot point for rotating the labels on the XAxis is the center of the label itself. Add the ability to change the pivot point to be the first symbol of the label.
For the time being the property can be set via the kendo object (http://docs.telerik.com/kendo-ui/api/javascript/dataviz/ui/chart#configuration-categoryAxis.labels.rotation.align):
		<script>
			function load(chart) {
				var align = "end"; //"center"
					chart.get_kendoWidget().setOptions({ categoryAxis: { labels: { rotation: { angle:45, align: align } } } });
			}
		</script>
		<telerik:RadHtmlChart ID="RadHtmlChart1" runat="server" Width="600" Height="400">
			<ClientEvents OnLoad="load" />
			<PlotArea>
				<Series>
					<telerik:ColumnSeries Name="Series 1">
						<Appearance></Appearance>
						<SeriesItems>
							<telerik:CategorySeriesItem Y="30" />
							<telerik:CategorySeriesItem Y="10" />
							<telerik:CategorySeriesItem Y="20" />
						</SeriesItems>
					</telerik:ColumnSeries>
				</Series>
				<XAxis>
					<LabelsAppearance></LabelsAppearance>
					<Items>
						<telerik:AxisItem LabelText="Item 1" />
						<telerik:AxisItem LabelText="Item 2" />
						<telerik:AxisItem LabelText="Item 3" />
					</Items>
				</XAxis>
			</PlotArea>
		</telerik:RadHtmlChart>

It would be helpful to have a way to set the major tick step value via the RadHtmlChart control.  This can be set on the client side, but it seems like a missing feature since I can change the major tick size and label step values via the control axis attributes.  Here's an example with my suggested attribute shown in comments on the xAxis below.

<telerik:RadHtmlChart runat="server" ID="RadHtmlChart1" DataSourceID="RequestDays">
    <ClientEvents OnLoad="OnLoad" />
    <PlotArea>
		<Series>
            <telerik:AreaSeries Name="Last Year" DataFieldY="Last"></telerik:AreaSeries>
            <telerik:AreaSeries Name="Current Year" DataFieldY="Current"></telerik:AreaSeries>
        </Series>
        <XAxis Name="Days" DataLabelsField="Days" MajorTickSize="5"> <%--MajorTickStep="7"--%>
            <LabelsAppearance Step="14" /> 
		</XAxis>
    </PlotArea>
</telerik:RadHtmlChart>

<script type="text/javascript">
        function OnLoad(chart) {
            var widget = chart.get_kendoWidget();
            widget.options.categoryAxis.majorTicks = { step: 7 };
            widget.redraw();
        }
    </script>

For the time being the following events can be handled through the chartObject.

Select event is fired when the range of the selector from the navigator pane is changed.

JavaScript:

    <telerik:RadCodeBlock ID="RadCodeBlock1" runat="server">
        <script>
            function pageLoad() {
                var chart = $find('<%=RadHtmlChart1.ClientID%>');
                chart._chartObject.bind("selectEnd", OnSelectEnd);
            }

            function OnSelectEnd(e) {
                alert("OnSelectEnd triggered: \nFrom: " + e.from + "\n To: " + e.to);
            }

        </script>
    </telerik:RadCodeBlock>
ASPX:

        <telerik:RadHtmlChart runat="server" ID="RadHtmlChart1" Layout="Stock" Width="800" Height="400"
            Transitions="true">
            <PlotArea>
                <XAxis Name="mainAxis" DataLabelsField="SellDate" Type="Date">
                </XAxis>
                <Series>
                    <telerik:ColumnSeries DataFieldY="SellQuantity">
                    </telerik:ColumnSeries>
                </Series>
            </PlotArea>
            <Navigator Visible="true">
                <XAxis Name="navAxis"></XAxis>
                <SelectionHint Visible="true" />
                <Series>
                    <telerik:AreaSeries DataFieldY="SellQuantity">
                    </telerik:AreaSeries>
                </Series>
            </Navigator>
        </telerik:RadHtmlChart>

C#:

    protected void Page_Load(object sender, EventArgs e)
    {
        RadHtmlChart1.DataSource = GetData();
        RadHtmlChart1.DataBind();
    }

    protected DataTable GetData()
    {
        DataTable dt = new DataTable();

        dt.Columns.Add("ID", typeof(int));
        dt.Columns.Add("SellQuantity", typeof(int));
        dt.Columns.Add("SellDate", typeof(DateTime));

        dt.Rows.Add(1, 2, new DateTime(2011, 06, 12));
        dt.Rows.Add(1, 5, new DateTime(2011, 12, 12));
        dt.Rows.Add(2, 6, new DateTime(2012, 06, 17));
        dt.Rows.Add(3, 4, new DateTime(2012, 09, 18));
        dt.Rows.Add(4, 7, new DateTime(2013, 03, 18));

        return dt;
    }

The OnClientPlotAreaClicked event could be similar to the OnClientSeriesClicked event. It might be used for charts which are very small in size and clicking an individual series is not so easy. For the time being the following workaround can be used:
ASPX:
		<script type="text/javascript">
			function pageLoad() {
				var chart = $find("<%=RadHtmlChart1.ClientID%>");
				chart._chartObject.bind('plotAreaClick', plotAreaClick);
			}

			function plotAreaClick(e) {
				if (e.originalEvent.type === "contextmenu") {
					// Disable browser context menu
					alert('rightClick');
					e.originalEvent.preventDefault();
				}
			}
		</script>
		<telerik:RadHtmlChart runat="server" ID="RadHtmlChart1" Width="600px" Height="400px">
			<PlotArea>
				<Series>
					<telerik:ColumnSeries Name="Product 1">
						<SeriesItems>
							<telerik:CategorySeriesItem Y="15000" />
							<telerik:CategorySeriesItem Y="23000" />
							<telerik:CategorySeriesItem Y="10000" />
						</SeriesItems>
					</telerik:ColumnSeries>
				</Series>
				<XAxis>
					<Items>
						<telerik:AxisItem LabelText="1" />
						<telerik:AxisItem LabelText="2" />
						<telerik:AxisItem LabelText="3" />
					</Items>
				</XAxis>
			</PlotArea>
		</telerik:RadHtmlChart>

The current implementation of RadHtmlChart explicitly specifies font-family and font-size settings on the server-side, which are then serialized and used by the Kendo widget, so the skin-specific settings are ignored.

For example, the Material skin should define a "Roboto" font-family, but this is overriden by "Arial" in the final serialization, so the skin configuration does not have any effect.

The default values of the server-side font settings can be removed in order to allow such customization and can be defined in the skins file instead.