Oh, as well as it being easy to get your book in whatever format from them, their customer service is good. I was a goofy person and impatient, so I emailed when my book hadn't shown up in the Kindle docs after a couple of minutes. Well, as soon as I sent the email, the book appeared. Heh. I sent another email right away saying thanks and never mind but the book came through. Well, I got a nice little email response saying they were glad the book came through and happy reading.
Anyway, they are good. Just access the site through Firefox or Chrome, not IE.