Autodesk: sketch book x

So my wife surprised me for Christmas with an iPad, the first thing I did of course was download a sketching app. I went with autodesk's Sketchbook Express. So far its not bad, I wish the touch screen was a little more sensitive to the stylus, so that the lines would turn out smooth and naturaul. Here are two sketches I did yesterday. I like being able to just working on character poses and proportions, but I'm starting to like over laying actual pictures with line work and blocks of color.