I never have hidden my email address, and I've never used a spam filter. I used to get a lot of spam, maybe 50 messages or so a day. Back when I got that many, I was sort of motivated to set up a spam filter... but I still never got around to it. These days, still unfiltered, I only get 2-5 a day, and I think (for me at least) setting up a spam filter is a waste of time. I guess all the cracking down on open relays and filtering SMTP etc. has done the trick?