http://blogs.msdn.com/jmanning/archive/2005/10/24/484153.aspxI've had 2 of my ISV buddies ask me this, so I'll provide the link here that I have to them: http://msdn.microsoft.com/netframework/programming/breakingchanges/default.aspx On a fully-unrelated note, as Buck mentioned , the TFS Beta3 VPC image (with allen-USCommunityServer 2.1 SP1 (Build: 61025.2)