Audible UK have released an app for the iPhone. The best feature over the built in software is that it doesn’t rotate when you hold it sideways (I am certain this “feature” of the the iPhone exists solely for in-store demos, I find it very frustrating and wish it could be turned off).
Other features include the ability to download books over the Internet (but strangely, not 3G which would have been more useful), add bookmarks with notes, customise the length of time the rewind button goes back, a button-less interface for when in the car, and a sleep timer. Overall the user experience is much more suited to audiobooks than the default iPhone interface and I highly recommend it.
For those if you you haven’t discovered the joy of audiobooks, they are a great way to read while driving, doing household chores or just when your eyes feel too tired to read (I get that a lot since my job involves using a computer all day). If you like books then give them a try.
Now if only there was some kind of Kindle like device that would play audiobooks, but keep your place in sync between the audiobook and the eBook.