Well, so far it's pretty good fun for me (because I'm largely playing it with a 4-year-old boy), and amazing fun for the four year old. Who is largely inept, but tries hard, and doesn't notice when I help him with the difficult bits. He's so far badgered me, his father _and_ his mother into playing Kinect Adventures, Sports and whatever the driving game is.
I also have Dance Central, which I'm very much looking forward to, but is way beyond his abilities. Julie arrives tomorrow though, and I'm looking forward to playing it with her a _lot_.