The underlying Kendo Linear Kendo stopped rendering the track in 2014.3.1314 and, respectively, so does RadLinearGauge as of 2015.1.225

For example, the following snippet should render a wide, green, semi-transparent track, but it does not

			<telerik:RadLinearGauge ID="gauge" runat="server" Height="280">
				<Pointer Value="20">
					<Track Color="#5ca038" Opacity="0.5" Size="30" />
				</Pointer>
			</telerik:RadLinearGauge>

Workaround:

  1) Use   RenderAs="SVG".
  2)  Set 100% width to the gauge's wrapper prior the resizing
 
Use the solution below to make the control responsive:
     <table style="width: 100%;">
            <tr>
                <td>
                    <div style="width: 100%;" id="gauge"></div>
                    <telerik:RadLinearGauge runat="server" ID="RadLinearGauge1" RenderAs="SVG" Width="100%">
                        <Pointer Color="Gray" Size="10" />
                        <Scale Vertical="false" Min="0" Max="40">
                            <MinorTicks Size="20" />
                            <Ranges>
                                <telerik:GaugeRange Color="#D7E5D1" From="0" To="10" />
                                <telerik:GaugeRange Color="#EBE6D2" From="10" To="20" />
                                <telerik:GaugeRange Color="#F5D2D1" From="20" To="30" />
                            </Ranges>
                        </Scale>
                    </telerik:RadLinearGauge>
                </td>
            </tr>
        </table>
            <script type="text/javascript">
                var $ = $telerik.$;
                $(window).resize(function () {
                    $("#<%= RadLinearGauge1.ClientID %> > div")[0].style.width = "100%";
                    $find('<%= RadLinearGauge1.ClientID %>').get_kendoWidget().resize();

                });
            </script>

For the time being you can use the following workaround:

        <script>
            var pointerSize = 35;

            function pageLoad() {
                var gauge = $find("<%=rgEpmScorecard.ClientID%>");
                gauge._gaugeObject.options.scale.rangeSize = 25;
                gauge.repaint();
            }

        </script>
        <telerik:RadRadialGauge ID="rgEpmScorecard" runat="server" Skin="Metro" Height="99px" Width="100px">
            <Pointer Value="50" Color="Black">
                <Cap Size="0.5" Color="Black" />
            </Pointer>
            <Scale MajorUnit="10" Max="100" Labels-Visible="false" StartAngle="-45" EndAngle="225">
                <MajorTicks Visible="false" />
                <MinorTicks Visible="false" />
                <Ranges>
                    <telerik:GaugeRange Color="#ac1d23" From="0" To="16.67" />
                    <telerik:GaugeRange Color="#c26522" From="16.7" To="33.33" />
                    <telerik:GaugeRange Color="#d2b408" From="33.5" To="50" />
                    <telerik:GaugeRange Color="#b5be25" From="50.04" To="66.66" />
                    <telerik:GaugeRange Color="#0c833f" From="66.8" To="83.33" />
                    <telerik:GaugeRange Color="#0b6cb3" From="83.38" To="100" />
                </Ranges>
            </Scale>
        </telerik:RadRadialGauge>
        <script>

            var dataviz = kendo.dataviz,
                draw = dataviz.drawing,
                Path = draw.Path,
                DEFAULT_LINE_WIDTH = 0.5;

            kendo.dataviz.RadialPointer.fn._renderNeedle = function () {
                var that = this;
                var options = that.options;
                var minorTickSize = that.scale.options.minorTicks.size;
                var center = that.center;
                var needleColor = options.color;

                var needlePath = new Path({
                    fill: { color: needleColor },
                    stroke: { color: needleColor, width: DEFAULT_LINE_WIDTH }
                });

                needlePath.moveTo(center.x + that.radius - minorTickSize + pointerSize, center.y)
                          .lineTo(center.x, center.y - (that.capSize / 2))
                          .lineTo(center.x, center.y + (that.capSize / 2))
                          .close();

                return needlePath;
            }
        </script>

The following:

<telerik:RadLinearGauge runat="server" ID="RadLinearGauge1" width=100%></telerik:RadLinearGauge>

will result in the width being set as 100px

Label for the Gauge range in the RadGauge control.
Apart from the individual points, need ability to name the range.

You can do this with the Template property of the Label object

			<telerik:RadLinearGauge runat="server" ID="rlg1">
				<Scale Min="1" Max="4" MajorUnit="1">
					<Labels Template="#= getLabelText(value)#" />
				</Scale>
			</telerik:RadLinearGauge>
			<telerik:RadRadialGauge runat="server" ID="rrg1">
				<Scale Min="1" Max="4" MajorUnit="1">
					<Labels Template="#= getLabelText(value)#" />
				</Scale>
			</telerik:RadRadialGauge>
			<script>
				function getLabelText(e) {
					return "label for " + e;
				}
			</script>

For old versions the template can be set through the kendoWidget:

ASPX:

        <script>
            function setGaugeLabels(value) {
                switch (value) {
                    case -10:
                        return "Min: " + -10;
                        break;
                    case 35:
                        return "Max: " + 35;
                        break;
                    default:
                        return "Name: " + value;
                        break;
                }
            }
            function pageLoad() {
                var gaugeObj = $find("<%=RadLinearGauge1.ClientID%>")._gaugeObject;
                gaugeObj.options.scale.labels.template = "#=setGaugeLabels(value)#";
                gaugeObj.redraw();
            }
        </script>
        <telerik:RadLinearGauge runat="server" ID="RadLinearGauge1" Height="300px" Width="100px">
            <Pointer Value="11" Color="Green">
            </Pointer>
            <Scale Min="-25" Max="50" MajorUnit="15" MinorUnit="1">
                <Labels Format="{0} °C" />
                <Ranges>
                    <telerik:GaugeRange From="-25" To="-5" Color="Blue" />
                    <telerik:GaugeRange From="-5" To="15" Color="LightBlue" />
                    <telerik:GaugeRange From="15" To="30" Color="GreenYellow" />
                    <telerik:GaugeRange From="30" To="50" Color="Red" />
                </Ranges>
            </Scale>
        </telerik:RadLinearGauge>

It would be nice if RadGauges, the radial ones especially, could include a title element

Expose an additional property in RadGauge that controls the margin for the gaugeArea.

As a workaround the width of the range placeholder can be set through the gaugeObject:
JavaScript:
		function pageLoad() {
			var gauge = $find("<%=RadRadialGauge1.ClientID%>");
			gauge._gaugeObject.options.scale.rangeSize = 30;
			gauge.repaint();
		}
		<telerik:RadRadialGauge runat="server" ID="RadRadialGauge1" Height="350px" Width="350px">
			<Pointer Value="220" Color="Black">
				<Cap Color="Gray" Size="0.1" />
			</Pointer>
			<Scale Min="120" Max="300" MajorUnit="30" MinorUnit="5">
				<Labels Format="{0} °C" Position="Outside" />
				<Ranges>
					<telerik:GaugeRange Color="Orange" From="150" To="190" />
					<telerik:GaugeRange Color="Green" From="190" To="230" />
					<telerik:GaugeRange Color="Red" From="230" To="300" />
				</Ranges>
			</Scale>
		</telerik:RadRadialGauge>

Add border and border appearance options like color, width and type for the RadGauge. Currently the background color of the RadGauge is set to the wrapper of the control. Improve that color so that it fits in with the border and the shape of the control.

If the gauge must display a huge range of values (e.g. Min=0, Max=500 000) having visible MinorTicks blocks the browser and ultimately throws an "out of stack space error".

The workaround is to set 
MinorTicks.Visible = false 
or Scale.MinorUnit to a sufficiently large value. If the minor unit is not set properly the minor ticks will clutter together and will be unreadable.

There are some issues with the appearance of the gauges in RTL mode. They vary across browsers.

An easy fix is to add a CSS class to each of them and force direction: ltr:

<telerik:RadRadialGauge CssClass="rtlFix" ID="radialGauge1" runat="server" Width="272px" Height="272px">
    . . . . .
</telerik:RadRadialGauge>

.rtlFix
{
    direction: ltr;
}

If you need to swap the places of the min and max value the Reverse property of the Scale inner tag must be set to true.

Similar to kendo gauge's functionality:

http://demos.telerik.com/kendo-ui/linear-gauge/multiple-pointers

http://demos.telerik.com/kendo-ui/radial-gauge/multiple-pointers