I've been using SpamAssassin quite successfully for a while. I think part of the key to success might be using the right combination of rules. My spam has been reduced drastically. Maybe 2-3 spam messages actually make it into my mailbox daily. I save those, then add rules for them to my custom ruleset. YMMV

As far as the regex you are looking for, you might get some ideas by looking at some of the rulesets at SARE Rules Emporium. There are many rules that deal with the various obfuscations of messages you're trying to keep out of your email.

Thanks,
Mike