I have had one now for about 6 months and it is really good as I got it with my 250gb xbox and it simply plugged into the socket in the back of the xbox with the orange bar on it. Also, it said I had position it so far away from the screen (can't remember the distance exact but top of tv or bottom...
Tracks you quick; better than the old xbox camera; good if you like dance games
Expensive; you need a lot of space (e.g big bedroom or lounge); can sometimes glitch; voice control isn't that great