Virus Bulleting evaluated 15 anti-spam vendors this month. I would love to post the pretty picture where they plot the vendors on a scale of spam catch rate vs false positive rate but I don’t think they would approve. You can sign up to get a copy here.
The formula for the final scores was the catch rate minus three times the false catch rate. Only five scored higher than 98% and one scored above 99%, which was M86 Mailmarshal. Of course this is on the VB test set. Your mileage may vary.