Fun for the whole family
I played this with my 4yr old daughter on an almost daily basis for months. It's intuitive enough that she quickly grasped the fundamentals - she has trouble with the pace of combat, but basic gameplay is enjoyable for her.
It looks great and I enjoy the simplicity and pace of the game. Some people have complained that it's not Zelda or whatever, but to me that's an attractive quality. I wanted something easy to play, but fun and bright enough to capture my child's attention. Kameo is a great family game.
If it was just me however, I suspect this would be a rental. You can finish it in not too many hours and if it wasn't for my daughter I wouldn't have been motivated to go back and do it again... I've never found all the secrets in any game, just not obsessive that way.
Note that one of the boss battles is super annoying even when you know exactly what you have to do; as with most console games of this type perseverance and a little luck is the key.