A Media Player thats suited for audio books would be first priority (especially since being able to play mp3 files played a big part in my decision to buy the 602).
The current media player is missing:
1) the ability to navigate an mp3 file (i.e. move back/forward in varying jump sizes)
2) the ability to auto-pause after a specified time with no interaction (so you don't wake up with the battery drained)
3) the ability to remember your place in the book (which mp3 file and where in it) even if you leave the player or shut down the device (people don't listen to a whole book in one sitting)
4) the ability to remember/save the playlist , part of the failure in 3 is that the player doesn't actually remember anything and when you launch it again it searches again.
5) being able to choose where to look for files and re-order the playlist (right now it'll add every mp3 file it can find to the list)