I'm trying out postfix-gld, a greylisting daemon which uses mysql and is available in the debian repositories. It looks pretty good. I'm willing to try something new (I use postgrey in production) as I'm setting up a backup MX.
While I'm at it, I'm also examining postfix-cdb.
UPDATE: I finally got postfix-gld to work, the hang-up was my own dumb typo, but its working now. It looks good too, I think it will make managing greylisting a lot easier, especially when it comes to multiple SMTP hosts. It would be nice if there was the option to set a different host for reads and writes, so that MySQL replicants could be used, but maybe that will be an excuse for me to explore MySQL proxy some more.