Got into playing it a bit more yesterday - Kinect Sports is great! Loving the discus throws and hurdles. Bowling is brill, too. The Track and Field section is over pretty quick, but you still manage to get a bit of a sweat on!
Also, in the Boxing game - try endlessly windmilling your arms. I nearly died laughing.
Joy Ride is good fun now that I've figured out drifting etc. I don't find it as unresponsive as some of the reviews have made out, either.
One thing we've found, through, is that Kinect HATES my wife, LOL. The facial recognition just doesn't like her at all (might be her glasses), and the body tracking in Kinect Sports definitely doesn't handle her as well as it does me - the Javelin and Discus being prime examples of where it works OK for me, but spazzes out and throws early etc. for her.
Lighting seems to be pretty important for it to function properly, and it also isn't too keen on the dog wandering around the room - tends to make my avatars legs go all "Riverdance" when he's puttering about.