I absolutely love ABB, and it makes my commute so much more painless. That said, I'd like to request a couple of features I haven't noticed posted before (but maybe I missed them).
The 12-hour limit is a little troublesome, especially when the length is barely over that limit and then I have a 1-chapter final part. Might I suggest (since I recall reading that the 12-hour limit was a feature you implemented rather than being required by iTunes or any iPods), that there be a preference to set how many hours the files should be broken into? I noticed someone else wanted them broken into CDs - this would solve his problem too, if he set it to 74 or 80 minutes, or something like that.
I've found a minor UI nuance that gets a little annoying. When expanding the detail view from the Chapters section, the window's bottom slides down, but when you change between views (Cover, Chapters, or Finish), the screen's top slides down. I think it would make sense for it to expand or contract in the same direction everywhere (I think what bothers me is that the titlebar/menu area moves atypically of other OS X programs - it should be the bottom edge that always moves).
I'm not sure if this is possible or easy, but it would be very useful to be able to boost the volume output at the time of conversion (finalization) with some kind of preview of the new level. Some of my files are pretty low, and when I adjust their Volume Adjustment level in iTunes, they end up distorting pretty badly. I noticed in QuickTime (not sure if you use that for conversion) there's a setting on files' audio tracks to boost the volume by up to 6 db. That might be useful.
[*}I think it would be pretty nifty if you could use Xgrid to convert multiple chapters concurrently across the computer's multiple cores. VisualHub (RIP) used to do this, and it was very useful on my dual- and octo-core machines.
Thanks for making such an awesome and useful product!
Lots of good suggestions in this post - but the one that's near my heart is the UI nuisance: resizing the window between views is bad enough, but that it's the title bar that moves makes it truly annoying.
I also wish that deleting files from the Chapters view didn't prompt a confirm dialog (or was an option I could set). I find anything that requires me to take my hands off of the keyboard in order to move the cursor annoying.