I was running my own Postfix server with spamassassin until I got frustrated (that was when I working for Google on Gmail spam/abuse and realized just how much better a job you can do with more resources and that there's no way I could come even close to that quality of filtering with my homegrown solution). Nowadays I run everything through Google. Sadly (?) this also saves me a ton of time and money (I sometimes miss tinkering with my mail setup).