My MCE machine
it's only a shame that you can't create multiple machines under once account (would make it easier to manage a profile) but I guess if I wanted to track the laptop, the MediaCentre and the office machine together I could set up three accounts and put them together in their own league.
Shame they don't have an OSX client yet (they only have Windows and Linux options) - would help answer the question of which platform is most stable ;)
Of course, the real shame is that WinXP and OSX even after all these years of tweaking and architecting still require reboots after patching/upgrading and (even worse) installing/uninstalling programs. I can't remember the last time I rebooted for the fun of it, but a couple of times in a day because of an installation and a WindowsUpdate session is just frustrating.