I enabled TypePad AntiSpam on my blog a few weeks back, and I've been extremely pleased with it.
Over the past three weeks, about ten spam comments a day have been getting through the filter (and going into my comment moderation queue). Before the antispam system, I was getting hundreds a day, at least.
On December 16, right around the time when things got so bad that I turned off comments entirely for a while, I got over 1600 pieces of comment spam in 24 hours, and those were just the ones that got through the spam filter I was using.
So thanks, TypePad!