DS1 has an innotab. He got it when he was around 2 1/2 I think. For the longest time I thought it was a total waste of money, as he preferred to play on my kindle or phone, since they are much more responsive and quicker. He also struggled for a while with the actual games being either too easy, therefore boring, or too hard if he tried to go to the next level. There really wasn't an in between level. It was beginner or advanced. He's 4 yrs old now, and has actually all of a sudden started wanting to play the games on it a lot lately. I think he just may have been too young for it before to really get the instructions to the games (they explain at the beginning of the game what to do), and didn't understand why it wasn't as responsive either. Now he knows he just needs to give it a little more time than my phone. I'm actually shocked at this sudden interest in it, and glad it is finally getting some use for all the money that was put into games, rechargeable batteries, etc.
Having said all that, if I could go back, I would have just gotten him his own tablet, and put parental controls on it. I think he enjoys playing the educational games on my kindle much more than his innotab, because they respond so quickly to his touch. And kindle games are free or only a few dollars, whereas the innotab games cost me $25 a piece.