After years of resisting using Gmail for email (I still have an original early beta account), the everyday use of my Android powered TMobile/HTC G1 has made the push-email integration with Gmail too tempting at last, and I’ve switched my email use from a dedicated IMAP account over to Gmail.
However I’m not trusting GOOG completely with my mail use, and to make sure absolute available of all my latest mail, and my back archive of emails in case I ever want to move this is my current setup:

1. Email goes to my personal domains, in which the MX records point to my dedicated server.
2. Postfix runs these emails through greylisting (using greyfix) and SpamAssassin just to stop any barbarians at the gate.
3. Postfix then forwards these emails to various local dynamic maps, which in turn forward to both my Gmail account and an offsite backup IMAP account.
4. A cron’d script on my server periodically deletes emails from the offsite backup IMAP account every 2 weeks, meaning I can get access to the last 2 weeks of email as well as send email out from my personal domains (I can also do this from my server, obviously, for outgoing) if there’s ever a Gmail problem.
5. Larch is also run every week to synchronise any emails in my Gmail account with a local IMAP archive, for future portability.

The upshot of this is that I get perfect webmail, desktop IMAP and push-email on my G1 without worry of any reliability on the GOOG. w00t.