I did not establish an account on the suggested audiobook sites because I don't listen to audiobooks. I've tried with cassettes and cds, but the experience leaves me irritated and rather bored. I love to read but an audiobook is not a format that I enjoy. I like to listen to music.
Personal preference aside, I think it's incredible that technology has advanced to the point that one can download an entire book. I think Gutenberg would just marvel over such an invention!