I just installed Adobe Ideas on my iPad, this app is pretty cool for sketching ideas and visual thinking and seems to provide the right balance between digital features (undo, rotate, zoom, etc.) and the best analog tool ever (your hand). I'm convinced that the introduction of the iPad is the kick-off for a major change in the way we interact with personal computers, I'm so frustrated when I touch the screen of my MacBook Pro and there is no effect... :-)