Hi, John (and Jim, if you're around).
I finally went back to SpamNet, but I downloaded it again, this time the latest version. Now it is quite faster. And it keeps doing it's job perfectly.
Indeed, they added a new feature that tell you your own rating as a SPAM detector (how reliable your informed SPAMs are). This is a measure of how their weighted algorithm works...
I really encourage you to try it. I think this is the best solution available, and it is almost entirely transparent. The product is now commercial but the cost is almost nothing, and they have a 30 day trial to let you check ist accuracy.
By now, I'm out of SPAM again.
Thanks a lot to everyone contributing to the thread!