My mate got his delivered today (Monday that is) and I've just spent the evening acting like a flailing tard :rasp:
It's pretty fun, and very knackering.
I can see the Dance Central game being pretty popular with the teens, not really my cup of tea though. The fitness one is pretty interesting, but the demo only had one quick thing with punching blocks. Kinect Adventus has some fun games, though you need quite a lot of space to play 2 player.
You're gonna need to be at least 6 feet back and preferably further, and you need at least a couple of feet behind you as well. Not one for cramped rooms at all.
It does spazz out sometimes and won't follow your movements, but if you step out of the camera area and back in it resets itself.
Some of the menu gestures are very Minority Report though which is pretty cool.