FYI, in the interest of eating my own dogfood, I've updated this site to use the Drupal fork Pressflow. I'm going to see what can be done to improve this site's performance and will document what I find.

As a brief follow-up to my post about dealing with spam on Drupal, the problem I had with Mollom turned out to be purely in my site configuration. Apparently some of the configuration changed from the previous version I had been using, so as soon as I re-saved the settings it all started working correctly again! I'm happy to say I haven't seen any spam come in during the past ten days and Mollom is the only anti-spam engine I'm currently running.