These are just toys!
I thought you were going to present the real interesting controller apps that is possible with for example an ipad.
I mean, for the average musician there is absolutely no point in using an ipad or an iphone in itselft as a software instrument. The quadcore monsters that are around (for both mac and pc;s) are more than enough for that.
But, being touchscreen, it is the ultimate controller for anybody who is serious about his home studio. Controlling mixer faders, knobs on the synths that are played from the computers, starting, stopping and so on...
Would have liked to have seen these types of pro-apps, which really are big, big selling points for the ipads (or android tablets) if they work well.
Almost the only thing that can ONLY be done on a tablett much better than on, for example, a notebook!