If any of you needed some hard evidence of what AudioBus - the new inter-app audio streaming protocol on iOS can do, this video should give you an idea of what is possible at a basic, one-app-records-another way.
The two apps being Loopy HD from a Tasty Pixel (co-founders of AudioBus) and Sunrizer from Beepstreet (also Impaktor - winners of the Sonic Touch Gold Award) - a great synthesizer for iOS.
AudioBus can also be used (theoretically) to process one applications audio in realtime through another - which will mean a whole bunch of new and exciting ways to route and process.
It is yet to be tested in the wild to any great degree, so we dont know who much CPU is eaten up, but its looking good.
Gaz Williams has one and he brought it round