I think this is going to prove to be an extremely useful and popular machine. While it would be fun to set it up with BlueTooth keyboard and mouse and hook it directly to the TV and stereo as an effective DVD player, games machine, photo browser, iTunes jukebox, watching DivX movies or hooking it up to an iSight and using it for video conferencing. The specs are just right for all of these tasks.
And if you're into home movies and don't allready have a DVD writer, then the SuperDrive upgrade and the included iLife '05 will let you just plug in your DV camera and burn straight to DVD.
For programmers and other techie types, it represents a great new toy that can be put to use in a lot of clever ways. Website developers from the Windows world might consider a Mac Mini and a KVM switch as a handy way of testing sites out on various Mac browsers. It would make a nice box for a Linux fan to muck around with, too, and would be handy for kiosk applications as well.
All up, very tempting, very cool -- though I'll probably be putting my cash into two "work related" items from the show: iWork and iPod Shuffle. ;-)