The WPF and Silverlight Gauges are pretty in the demos but I must say they are a real pain to get started with. I have been using various gauge products in my applications for years and I think yours look great and operate great but to use them in your code really is a pain.
With great customizability comes great pain.
I think you would do your clients a big favor if you provided a Gauge designer. So that I can via a UI build out the XAML required for my Gauge. Start out with a high level Linear, Radial..etc and allow me to tweak some (not all) of the properties to make it into a gauge that I want in my application. Then allow me to cut and past the Gauge XAML into my code or do the paste for me. I think that would make your tools a million times better.
Another comment, somewhat related. Your demos have source code behind them so it is possible for a developer to take some of the code modeled in your demo and use it in their app. However your demo's use custom classes (whilst the code is written very well) it obfuscates what is happening. Because of this and your extremely limited documentation for WPF/Silverlight there is a great barrier to using your products. Wizards like the one I explained would help out a lot. Clearer documentation would also help greatly. An example of a shortfall in your documentation is this: I want to databind to a RadGridView but do not want to use AutoCreateColumns. You have no documentation on it. To me, AutoCreateColumns is not a real world feature but Custom Columns are.. there is documentation on the prior but not on the latter. One more note on WPF documentation. Create basic examples instead of massively complex examples. For example, do not use Control Templates and Styles in your basic examples (unless you are giving an example of such). This only confuses a WPF/XAML newbie and can turn them off of using your product. Maybe in a year it will make sense to elevate past some of the XAML/WPF basics but at this stage of the game I think it is good to show straightforward examples and add on to them in more advanced examples.
Anyway, I have been a Telerik customer for many years (across many of my clients) and I love your products. I just wanted to provide you some feedback in these areas that I consider deficiencies.