Part of me wonders why you'd want to program on an iPad. But it also feels like the kind of thing I'm being close minded about. Does anyone have good stories of this working well or being nice in some way I don't anticipate?
Acgourley, good point. It's very useful when making small changes to an application in the field. The Dropbox integration makes it easy to write a sketch on your computer and then to modify it on-the-go with iOS. One example: If you have Bean sensors throughout a large space, it's easier to visit the installed sensors, interact with, and update them using the mobile device.
