Wow. It's innovative, easy and stable (on my mac). I don't think it really is necessary to be able to save the mixes. It works like a JamSession.

What really needs to be done:

1. Make the mainView a SubView to ScrollView (so you can scroll in the window)
2. It cries out loud for other cool items: filter, tempochange, pitchshift, ...
3. Make it OpenSource, so others can make improvements to this app

btw: don't forget to visit the homepage of AudioPad: http://web.media.mit.edu/~jpatten/audiopad

Excellent start of a new kind of audio software.
And please: Keep this free! :-)