BTDT and it was a huge relief when I moved my domain to Google Apps and started using Gmail. Unless it's gotten hugely more effective than it was a few years ago, Spamassassin is nowhere near as good as Gmail at recognizing spam, and spamfighting was the biggest of many chores involved in running my own server. I was constantly having to tweak and refine things to keep my spam filtering effective.
I don't miss running my own MTA. At all.