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.

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.

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 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.

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

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;

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.