I'm running ATA and WP 2.7 on several sites. My main site is my newspaper, and the theme has gotten a lot of customization. I'm afraid of upgrading to WP 2.8 and/or the next version of ATA. Since this question and answer might be useful to others, I've posted here instead of IM'ing Flynn.
Other than just doing a database backup, what would be the best way to approach such an upgrade?