Brian Harry just announced that the upcoming R3 release of BizTalk Server 2006 is going to have support in the TFS Team Build.
For the couple months now, we have been building our BizTalk solutions in our build server using only the devenv.exe. But it's a really pain in the *backside* to put it to work. We're managing, but this announce really made us (at least me) smile :)
Until next time ;)