If you haven't upgraded your Wordpress installation to version 2.9 yet, you might want to consider doing that soon. There are quite a few improvements, bug fixes and security features available in the new version.
The automatic upgrade via the admin interface actually worked just fine for me. Of course, I backed up my database and files first, just to be sure.
Do you run automatic backups on your mysql DB?
I run a simple PHP script via cron every day that uploads my under 1 megabyte database automatically to Cloud Files. It names it something like kgato-January-3-2010.sql so it's easy to find the backup I want.
It's nifty, not going to lie.
On topic, the automatic upgrade has always functioned perfect for me (: of course always back up. Wordpress really has their act together. (Personal opinion) Interested in where the system will be a year from now.
-Kyle