Did you see this video http://www.youtube.com/watch?v=NAllFWSl998&feature=player_embedded ? Very interesting. Really, Atomic Tom Live become iPhone in music.
Embedded: Saw Virtuoso Piano and iShred, didn't recognize the drum kit or what they were singing into. It's pretty easy to jam with a handfull of iDevices - my wife and I play around with iShred/Guitar, NanoStudio, ThumbJam and a handful of other apps in little impromptu jam sessions when we're bored.
I adore Virtuoso Piano application as it is one of the most amazing app, which combines the traditional piano with the latest tech. It gives me a unique experience, taking me back to the nineties and remaining in the same era with iPhone in my hands. Classy!