I have a couple of audio books in audible format (www.audible.com)
It's basically telephone quality, about a meg an hour (I think).
However, their windows player uses all the idle processor power (killing the rc5 client), whilst the realplayer plugin seems ok, so they might have an optimisation problem somewhere... =)
It might make a nice empeg plugin at some point...

Jazz
(List 112, S/N 00030, 4 gig blue)