I’m not sure about iPad painting. There are instantly a number of limitations with it, the main one being (with the sketchbook app I use at least) that the degree of precision available when using a pencil or brush is just not there with the iPad.
But it does offer the excitement and anticipation of a new medium; it is also fun to play with. In any event it is here, and I suspect there will be a lot of iPad masterpieces emerging out there, just proving me wrong.