Apple released the 10.4.3 update today - a massive 56MB file through the software updater(97 MB for the standalone version) which purports to fix a gazillion things and the kitchen sink! The install was uneventful but I found the restart to be reallllly slow. Patience is a must on the first reboot. Everything seemed to work fine, except apple mail suddenly stopped processing the rules i had set up. Yikes!! I get so much email on a daily basis that this is a critical problem. I figured it was the add-ons to mail that was causing the issue and uninstalled mail act-on and mail tags (just remove the bundles from your home>library>mail>bundles directory), and as i suspected the rules began working again.
Another notable: Running a repair permissions after updating results in a huge list of repairs.