ZenBrush - $2.99
Found another nice drawing app for the iPad. Again it's quite limited in terms of features but it makes up for that with a really nice, speed sensitive brush mark. It only has three opacities of black and an eraser, no zoom, no layers and only one undo. But that makes it very quick and intuitive to use. Plus points are - there's not much lag, a beautiful brush and a few different paper options. I can see myself using this for sketching quite a bit.