I am really liking the Nokia Audiobooks application. Although the music player CAN be used to listen to mp3s of audiobooks, a specialized application here is very welcome. It is simple easy to use on the handset once you have he books loaded.
There is (sadly, Windows-only) an application to help load the chapters or books onto your device. Although slow, you can even transfer over Bluetooth, which is a nice feature I wish was in the Nokia Music client. Also, by having a separate application and loader, the audio files are in a different directory than your music. So no random chapters of Jane Austen when you simply filre up the music player and hit shuffle on all tunes.
I appreciate this separation, however, I would like to see integration into the Nokia Music app, just so I could do everything in one place. Hopefully the Nokia Music folks will take a cue from the Audiobook developers and use the regular PC Suite connection and allow transfers via bluetooth!