When American Gods was released in print, I was lucky enough to have the first chapter read to me by Gaiman at a signing, and it was fantastic to listen to him read that much of it. But the thought of lugging around multiple CDs (which is traditionally how they come) for one lengthy novel puts me off the audio bit.
I have a copy of The Lord of the Rings trilogy on CD that is supposedly fantastic, but it's almost a spindle-worth of CDs and I can't get into it because of that--what a commitment. And I'd rather carry around a tattered copy of the book than spend the time ripping them to MP3s that I could dump to my iPod so I could have them on the go.
MP3 format should make the audios involve less discs... and that appeals to me. BUT, I don't have an MP3 player in my car, so the disc would be ripped to my computer and dumped on my iPod for transport.
As an aside, Daniel Quinn's book Ishmael was given to me as a book on tape about 10 years ago. I wore it out listening to it and am now searching for another audio copy of that recording.
And I should probably also note that I am generally a very page-turning traditionalist when it comes to my reading...but audio adaptations/recordings do have their place.