I wanted to thank everyone who answered some of my questions in the last thread I posted. Since posting that, I've been hard at work creating ePub QuickLook and Spotlight plugins for Mac OS X.
If you're interested in helping me test them, I've posted a brief description of the plugins at
http://books.aetherial.net/wordpress/?p=217
These are early iterations, so please let me know if something isn't being indexed properly or if cover images are not showing.
Thanks again!