Personal Computer World in the UK (December 2003 issue) did an exhaustive competitive review of spam products including Spam Assassin and SpamBayes. You know what won? InBoxer. InBoxer (http://www.inboxer.com) is actually based on the SpamBayes source code, but some other stuff -- including technical support -- is added.
Personal Computer World gave it both the Best Buy and Editor's Choice Rating