I guess with its current status this doesn't need another 5-star rating, but I like it so much I want to give one anyway :-)

I use some e-mail addresses which have been around for more than 10 years and I get insane amounts of spam. E-mail would basically be unusable for me without SpamSieve.

It kills several hundred spam messages every day and it's months between false positives and I usually get a false negative once every few days. I am still amazed at how precisely it filters out spam.

Integration into Apple Mail is flawless.

The program is so rock solid and unobstrusive that I usually forget that it's there. Documentation is excellent but you'll never need it anyway. There are frequent updates and every version so far worked great.

I have been using this instead of the Apple Mail Junk filter for years and can highly recommend it.