I am an unwilling and unhappy user of Windows 8. I'm watching a series of course lectures as mp4 files, and the default video player is Xbox. It's fine, and a decent video player, but I need to switch back and forth between lecture and compiler, and often, the Xbox process will vanish from the Alt-tab list. Sometimes this happens a few seconds after switching away, sometimes I can go 20 minutes without it happening.
I could switch to WMP, but it's even worse. I'd like to get the Xbox video to work - it might make it feel like Win8 is not a complete and utter disaster. (Just an utter disaster ;)