since we had a lot of problem with your gauge (missing documentation as first thing) we decided to use other gauges in our silverlight applications.
We choose Dave's Silverlight Dashboard. (http://www.david-black.info/Bashboard/Default.aspx
The reason - free including sourcecode.
AND - most important - it takes only a few line of XAML to get a nice looking gauge.
These work fine - but only for silverlight.
Your controls (I guess from reading) have the same codebase for Silverlight and WPF.
So since we would need your controls primarily for WPF I ask in this forum.
The above noted controls allowe two-way data binding.
Do you (in the near future) also think about implementing two way binding?