This is a pretty interesting format. The iElectribe is majorly awesome-looking too, especially at $9.99 (intro price).
It was also recently hinted that the iPad will indeed support USB audio interfaces (http://createdigitalmusic.com/2010/04/14/apple-ipad-may-support-usb-audio-interfaces-via-camera-accessory-kit/#more-10543)
I'll wait and see if more apps become available before getting too hot under the collar for it. But a killer app for me would be a simple Traktor DJ Studio-type program. This way I could prepare my DJ sets & practice on the train/plane/whatever to out-of-town DJ gigs. I couldn't really imagine it as a laptop replacement for live shows - an iPad would probably sit somewhat precariously on an Ultimate Apex stand. But if it could run a good DJ program, and maybe sync up some virtual grooveboxes like the iElectribe (imagine if D16 made an iPad app!), I'd be well interested.
Anyone taken the plunge yet? Any cool apps to look out for or any apps on your wish-list?