David Teitlebaum has put together a set of perf guidelines which should help you get the most out of WPF3D on Tier 2 devices.

<Disclaimer> Before you go off and implement all of the tips be sure to profile your application to find out where the true bottlenecks are in order to get the most improvement for the least amount of effort. Furthermore, these are just guidelines that are generally true but in reality they may differ depending on the underlying hardware </Disclaimer> :)

In the future, we hope to expand upon some of the tips here on the blog. 

-- Jordan