Audible is pretty good. Can no longer justify such an expense, not on the student loans I'm living on these days. The library system I'm a patron of has everything, and I mean EVERYTHING, so that works just dandy for me. I'd say audible is worth the expense, if you have the disposable income (pennies in a bucket really) and voraciously love audiobooks.
The one thing I always hated though; buying a book only to find out the reader was crap. Nothing worse than a brilliant writer or his/her brilliant book being massacred by a "meh" reader (Packing For Mars by Mary Roach,
read by mutilated by Sandra Burr... They should have gotten Felicity Day or someone who was into the subject or who had at least read the book before the recording sessions. /rant) GRRRR.... And they don't have everything, and sometimes they didn't have the book I wanted being read by the reader I wanted, and found what I was looking for elsewhere, usually for free. So, there's that.