>Does anyone here use Audible.com?

No, but one of my co-workers does, and she's really happy with it.

I, on the other hand, am fairly happy with http://eMusic.com/. It trusts you to follow the law, and doesn't slap lots of artificial restrictions on your files. If you want to give it a try, you can get a free trial subscription, and download some 25 tracks: if you get an invite from me, I get an extra 50 downloads when you join. :-)