Hey check out the new action from the BizTalk Server Performance & Stress Team!

http://blogs.msdn.com/biztalkperformance/

The first blog dives into understanding the throughput and capacity of BizTalk Server 2004 SP1 and how to monitor and observe your system behavior.  Looks like they plan to provide a host of entries on optimizing, tracking, adapter performance details, host configuration, and lots more!