Alright i have the final release of Vista Ultimate installed on my machine here at work (msdn release) and doing some testing.
i've noticed now the old Windows Messenger WILL install and run (beta's it wouldnt install) but has known compatibility issues as i've noticed it will work for a while...
active directory
admin pack
admin toolscompatibility
crash issues
developer testing
internal messaging
live communications server
messaging
messenger
microsoft
operating system
sip accounts
toolscompatibility
trillian
user management
vista
windows