Excellent for transferring audio
AudioView fills a key gap in the iDevice audio market by allowing easy transfer between audio apps and devices. The feature I use most frequently is the ability to import from an email, then paste to the Audio pasteboard. Once I've done that I can easily import to another audio app like MultiTrack DAW.
Also incredibly useful is the ability to copy audio between iDevices, all without the use of a laptop. It's what has allowed me to create audio start to finish all on my iPhone or iPad. Great utility. Developer says that download from Soundcloud is coming too, which would fill another gap -- many apps support upload, but download is needed too to facilitate cooperation in music creation.
The UI is a little unintuitive, but again, then utility fills such a key gap that it ends up not being a big deal. If you need to move audio between apps, this app is the one to buy.
Update: still relying so heavily on this app -- Amplitube's new fender app still doesn't support copy/paste. So I export via email, open in Audio View, then paste into MT Daw. Great stuff.