At TechEd 2012 session DEV340 - Taking Your Application Lifecycle Management to the Cloud With the Team Foundation Service (which I recommend watching) the presenter mentions that TFS 2012 has been used internally at Microsoft for a while. This is described in further details at http://blogs.msdn.com/b/buckh/archive/2012/06/08/developer-division-is-running-on-tfs-2012-rc.aspx, where it is also mentioned that they are running with 3600+ users currently. I think (hope…) this will result in a more stable TFS, especially in Lab Management. Looking forward to get onto TFS 2012