I use my own MX rubber-banded together with Postfix, SpamAssassin, and dovecot IMAP. I also have bucket.mydomain pointed to mailinator.com so I can use addresses under that domain as throwaways without the site I'm signing up for knowing about it, although I also use Postfix aliases for long-term throwaways.
My coworker runs his own MX, but bounces all his mail through Google just for the spam filtering.