audible.com?

I got a promotional e-mail from Audible.com because I have an Amazon account, but I never paid them any mind before because I wasn't into audio books until a few months ago. But I went exploring today. I got my ooo-shiny Mulan face on (see icon) because Stephen Fry's books are there, and so are Cabin Pressure and two versions of Tinker Tailor Soldier Spy. But before I sign up and go nuts, I want to know a few things from those of you who use it. I can figure out how it works and all that; what's more important to me is how you like it and how user friendly it is.

Thanks in advance,

Kel