My kids got innotabs from my mom for Christmas, and they both love them. My 2 year old isn't quite so skilled with navigating around with it, but he can do some stuff on it. My 4 year old adores hers, and can do all sorts of stuff on it. I have no experience with the leap pad to compare them, though.
LO is 18 months and has a leap pad. We've put several books and videos on it so far and a few games but he is not really good at the games yet. The videos are really what interest him and it's good for when he's waiting at places.