Audio e-books: choices, choices!

I have been looking into audio e-books for a while now, experimenting a bit to see what might work best in my library setting. I have been unable (long story I won't go into here) to get into the downloadable models offered by Overdrive and NetLibrary (where patrons can download audio- or text- e-books to view/listen to on their PCs, PDAs, or MP3 players -- or in some cases burn them to CD). I've been looking at Playaway as a possibility. Playaway sells audio books as little MP3 players loaded with a single book. You can circulate them as single item (much as you would a print book) or you can also provide patrons with headphones or FM transmitters.

I see the plus with Playaway in that patrons who are not already comfortable with MP3 players do not have the hurdles of a) downloading the title, b) then getting the title onto their MP3 player, and c) getting the title to play correctly. Even with MP3-friendly folks, there are real technical support issues to consider on getting all the pieces to work together. With Playaway, though, will each title get enough use to justify purchasing it? The device is not reloadable at the library level, so if I really wanted three copies of Memoirs of a Geisha, and no one ever checks out How to Prevent a Robot Uprising (great read/listen, by the way), I can't wipe out the latter to accomodate another copy of the former.

Or, should I give up on any of these options because the titles are not the best fit for an academic library setting? We buy a fair amount of fiction and rent McNaughtons for popular reading, so this might not be that different. What do you think?