Popfile needs about 10 minutes set up and then training, which can be time consuming
I must say that blue squirrel "spam sleuth" worked pretty well out of the box although it worked better with more features tweaked, the config took a bit of time when adding sites and word filters. I works in layers, first using a combination of whitelists, blacklists, your address book, word filter rules (a lot of them come with it), character & structure rules, plus a bayesian training option (train on existing pots of email after about a week). What it does is use some of the cheap options to do a basic filtering, then anything in the "not sure" middle it can apply further tests, or do challenge response. It can also automatically complain for spam, but i turned that off.