Your RadDataFilter is great.  However, your documentation is lacking.  The control is not included in the SDK download and, the examples reference classes that aren't included in the documentation.  Look at the 
"Default Filter Editors" example.  In the example, you reference a behavior in the Example that has no supporting class and no way for me to see it.  Specifically, "Example.xaml":  behavior:MyFilterDescriptorBindingBehavior.FilterDescriptors="{Binding FilterDescriptors, Source={StaticResource model}}"