I really like Kinect, think it's great and always have done.
Automatically signs me in when I walk in the room (as well as the missus, and my mates). Same when I go to a friends, walk in his front room and I'm signed in.
Use the built in mic for voice commands all the time, using netflix, pause/play etc, shouting "xbox record that" after funny in game moments, turning the console on and off, switching between games/apps.
Xbox Fitness is great. I've been using it on and off since I got the console at launch. This year I've been using it much more and since the 1st Jan I've lost just short of a stone already (no other exercise, gym, running cycling, just xbox fitness).
I'm yet to get the Kinect Sports game but probably will at somepoint as I enjoyed the jetski demo.
I'm also tempted to get the Rabbids TV Invasion or what ever it's called. Usually good for a laugh with friends round.
Fruit Ninja on the 360 was awesome. Spent seleveral evenings having a few drinks with mates and getting all "karate kid" in the front room and looking like fools. Although almost kicking the radiator off the wall was bit of an issue lol