Just to add some anecdotal pain... I recently bought my first audio book from Audible. I didn't realise it was a proprietary DRM'd format which has no sensible playback on Linux. So rather than spend time hacking together something to rip it, I ended up torrent'ing an mp3 of the book I'd just bought.
It's entirely put me off buying anything else from Audible :-/
It's entirely put me off buying anything else from Audible :-/