Dustin Metzgar and Sajay Antony, our performance developers, have all started up their blogs on MSDN, which is great news to developers who are interested in WCF/WF/AppFabric performance or other fun things covered by their blogs.
Dustin has just started up his blog on MSDN. Dustin has great expertise on performance tools (such as xperf, VSTS profiler, CLR Profiler, etc). He also wrote the WF 4 performance whitepaper (see my previous blog).
Sajay Antony has his blog up a while back. He has in-depth experience on WCF performance and has done some solid performance improvements to the WCF/WF stacks. Here is one example.