Well, 'WPF' seems like a technology which isn't really adapted by developers. Partly I think because there wasn't really good design time support. In Java land, people often write their gui layouts in code, as their panel stuff is really powerful. With WPF you can do that too, but apparently people on .NET are locked into 'design time'
I think it will change in the (near) future as more control vendors come with their WPF libraries. We've planned to build v3 with WPF, at least parts of it.