I'm sorry, I believe the change log is only for updates and not nightly builds, correct? Is there a way to see what each nightly build fixes/changes?

You can view the changes in the nightly builds in SVN.

http://www.zenphoto.org/trac/browser/trunk

Definitely. Check out the Trac timeline for the day in question. The last 30 days of changes can always be seen at http://www.zenphoto.org/trac/timeline, and you can select only "Repository checkins" if that's all you want to see.

thanks!