Well, I'm not sure whether LeapPad have improved their art app, but they've improved the speed of the processor at the heart of the LeapPad 2. This will undoubtedly make not just drawing apps run slicker, but also many of the other apps and games. Apps should also load faster.
The best thing about LeapPad 2 is the new rechargeable battery. HOWEVER it's another $40 to add on the cost of the product. I didn't see it mentioned here so I thought I'd bring it up :-)
The latest LeapPads come with rechargeable batteries (with USB charging cables included), as did the first Ultra tablet. The older LeapPad 2 is battery operated, but you can buy a separate recharger pack at the LeapFrog store. The LeapPad2 Power and Ultra came with their own rechargeable batteries and adaptor.