For the time being you can position a style element with absolute position below the gauge cap that will store the current value of the gauge. See an example in the http://www.telerik.com/forums/some-questions-c37b45192cef forum post.

You can vote for this feature so that it must be implemented in the Kendo Gauge first http://kendoui-feedback.telerik.com/forums/127393-kendo-ui-feedback/suggestions/3692105-hi-need-a-label-for-the-pointer-shown-in-the-line
Once it gets implemented, it can be ported to the UI for ASP.NET AJAX Gauge server wrapper.

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

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>

This should also allow accessing them in the code-behind through their names and not only by their index, e.g.:

GuageName.Scale.Ranges[GaugeRangeName].From = value;

Currently RadGauge has an option to turn on/off the animation when the chart is rendered through its transition property. If that property is set to true the requested feature will allow setting the speed/duration of the animation. 

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.

I would like to consider the ability to customise the labels for the GaugeRange items that may not be part of a numerical index. For example, you may have a 3 range gauge that is low (green) / medium (orange) / high (red). Currently there is no way of customising these values.

I believe this would be similar to what is currently done in the Slider control ( http://demos.telerik.com/aspnet-ajax/slider/examples/slideritems/defaultvb.aspx)

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>

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.

Implement autoscale functionality to RadGauge

Currently only BarIndicator and Arrow are available. A line with contrasting color over the track, a double arrow, a circle, etc. can be other shapes built-in in the control.

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.

Currently the skins of the RadGauge contain predefined colors for the cap, pointer, track, major/minor ticks, scale labels and rangeplaceholder. Add the predefined colors for the ranges in the skins as well.

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

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