If you’re like the many folks who have asked us for a 'list of performance suggestions', your prayers have been answered. My colleague & friend Kiran Kumar, has partnered with the brilliant folks on our SDK team (Lorin in particular), to document as much WPF perf knowledge as they could come up with. Due to the high demand, Kiran has pre-released this tome of knowledge to his blog ahead of the final RTM SDK release.
This document is extremely impressive -- it's the most authoritative summary of WPF performance best-practices to date. Read this, internalize it, and apply it to your applications and they will run faster.