We have the LeapPad. We got it a few weeks ago for DS2. It's not the newest version - we got the older one for £45.00. Picked that over the Innotab because this has a camera and can make videos. This is apparently not a facility on the Innotab.
There was a thread on this site about it ( will look) and that helped me chose the LeapPad.
You can apparently set the games/apps it to the ability of your child. We have 2 games that we bought to go with it and then you can get Apps.
We haven't yet connected it to the internet - must do that this weekend.
Both my children (7 & 4) like it. They love the camera and making films of us.
Batteries - we put in some heavy duty ones. They lasted 2 days. Got an adapter which is useful. Going to get super-duper heavy duty rechargables.