Got that already - stopping approx. 100 users per day, 37884 Spammers blocked up until today in total as of right now.
That won't help with spammers posting as guests in those sectios that are open for them.
We also got a mod that only allows the posting of links to registered members with more than 3 posts (number is adjustable).
Besides that every guest post requires verification bty captcha.
we also got a banlist for spammers IP's with hits in the hundreds per day.