We've published a case study on our experiences of transitioning CodePlex from TFS 2008 to TFS 2010.  There were some pretty substantial benefits.  If you find yourself using some kind of shared TFS service and are contemplating upgrading to TFS 2010, I recommend you check it out.

http://www.microsoft.com/casestudies/Case_Study_Detail.aspx?CaseStudyID=4000008270

Brian