SpamAssassin Pro stopped working for me. I don't know why. The settings were screwed up, so tons and tons of spam wasn't being filtered, and when I click on settings, nothing happens. On two different computers. I wrote them about it, but they didn't reply (to that question). I tried to uninstall it, to try again, and it wouldn't uninstall. So now I'm trying Cloudmark, which I read about in Wired magazine, so it must be cool. We'll see. So far, it's on #409 of 2237 items in my inbox.
Update: The verdict so far is not good. Maybe the system, which relies on collaborative filtering, just doesn't have enough users yet, but today, SpamNet has caught about eight spams out of at least 50 that have hit my inbox.
Update Update: Oh, maybe it was a bad time to try it out: "Users of SpamNet, a popular peer-to-peer unsolicited e-mail filtering service, had grown accustomed to virtually junk-free inboxes. So when spam suddenly started pouring in last week, SpamNet users weren't very happy....But SpamNet hasn't brokered a deal with the e-mail devil. And the service, which is still in beta-testing, doesn't appear to be permanently broken."