I've just started using SpamBouncer to filter my mail. In a week, out of ~3300 messages (yeah, I get a lot of mail), it's yanked out about 1300 as spam, and only 10 of those were false positives. I've had a couple of dozen sneak through, but I like those numbers.

It's a great joy to wake up in the morning, open my mail client, and *not* have 30 or 40 spams sitting in the Inbox.