I beat Kameo the other day as can be seen on my gamer card. It was the first 360 game I played extensively. The game is a pretty standard platformer. It is probably the best looking game of its kind I have seen yet. It was a little short I think but not too much. There was a nice variety due to all the characters you could change into. The downside was that there wasn't as much use of the various characters as I would hope. I was looking for alternative techniques to solve puzzles, but in most cases you had to use a particular elemental. The boss battles were more endurance than technique. Even the final boss battle was simply move / shoot and really no other advanced techniques.
I tried the multiplayer a bit with my brother. Supposedly the first upgrade for Kameo will be live enabled multiplayer. I haven't unlocked any of the achievements for scoring an A on the levels. I am not sure I am up for redoing the levels again and again.
Overall I would say the game was a good launch title. The fact that it came out as good as it did is amazing especially considering its long and storied history across multiple systems and owners. I don't think it is ready to become the well known character for Microsoft like Mario, Sonic or Crash. I you have a 360 and like platformers it is recommended.