I dealt with my first comment spam with MT-Blacklist today! It didn't get caught by the default filter, but with a quick click on the blacklist link in the notification email, I added the offending URL to the list, and poof--the spam comment was magically removed. No tedious deleting of the comment, adding the IP and waiting for the site to rebuild.

If anyone wants to look at the blacklist of the banned URLs and regexes for the URLs, you can find it here.