- Email comes in to my default email box (myname@mydomain.com -- the names and domains have been changed to protect me from spammy behavior).
- Gmail is configured to retrieve all mail from that account via POP3. Mail is set to not be left on the server, so it is deleted when retrieved by Gmail. (Gmail actually does this for a number of mailboxes, so I also aggregate email from multiple addresses into one place, further simplifying my life.)
- Gmail is also configured to archive and forward all mail it gets to private54305849@mydomain.com -- a very random address which is highly unlikely to ever become one a spammer guesses or gets ahold of. (I never tell anyone about it, and no mail is ever sent from it. The actual number has been changed here, obviously.)
The downsides? Having the mail get bounced around twice could slow down my receiving the email in the first place. Howeer, I already follow much of the Get Things Done thinking in that I only check mail hourly at most, and refuse to live my life hanging on the immediate receipt of anything. If I get desperate for something to arrive, I can always try to login to the original first box and get the mail before Gmail does.
As an added bonus, I still have access to all of the mail in Gmail in case I want to do any searches, etc. And I filter my inbound mail in my own private3493849893 account, so the inbox has only non-list email for iPhone purposes, but I still can access the list mail in the other boxes on the iPhone if I need to.

