By lacking a keyboard, input and production aren’t quite as natural. That isn’t necessarily because the iPad can’t accommodate such input, but rather that the software–and our habits as users–haven’t completely caught up with the not-insignificant shift in interface.
Some interesting ideas for freehand use of the iPad. An assumption might exist here that everyone has one, but we know that is not so. What about network limitations, and students who can't afford to BYOD?
My kids have all created wonderful examples of web 2.0 presentations using this software, as early as the 2nd grade. If you haven't tried it, you should.