Pablo is one the most senior people on the WPF team and has been a key decision maker in deciding what scenarios WPF would address.
I'm going to call out one point in particular, because I see a lot of people, including internally confused about WPF 3D.
if you already have domain knowledge in Direct3D (or OpenGL), you should stick with using Direct3D for WPF v1.
Now, to provide more context on my guidance. We make 3D a lot easier to use in WPF, and by a much larger developer audience than the one that uses 3D today. We also make it usable on the Web (in a xbap), we make it print, we make it remote, and we make it easier to integrate 3D with 2D, UI controls, and Documents (including as part of XAML). But, in using WPF, you give up a bit of the flexibility and direct hardware control that you get with the lower level APIs. ....
We did not optimize our architecture in this initial version for twitch games or high end scientific vizualization scenarios, so if you want to tackle something along those lines, give it a try and see if it meets your needs.