Sketchbook Mobile

I recently picked up the Sketchbook Mobile app for my iPhone. I haven't decided if it is something that would be useful for me or if it is more of a nifty novelty app. The screen size of the iPhone definitely makes it less than practical, but if I buy a tablet to use as a digital sketchbook it's not going to be an iPad. I'd rather get something with some actual pressure sensitivity. This little guy was all of about twenty minutes of sketching and coloring. At the moment the app seems okay for rough loose sketches, but I'm finding it difficult to get any kind of clean line with out an awful lot of work. Guess I'll just have to keep fiddling with it before making any definitive decisions about using it to replace my physical sketchbook.