A couple months back I posted a blog on running OCS 2007 on XenApp. In it I highlighted a couple of known issues (doesn't support voice or video at this time), but I also posted a feedback received from customers that the user status changes intermittently. E.g., Communicator will change your status to "Away" even if you are online and available. If you have experienced this annoyance, it appears this issue (sporadic presence change) has been addressed in Microsoft's April 30^th update for OCS 2007. You can find more information about this update here: http://support.microsoft.com/kb/951662/