"Personally, I use Outlook 2007 to download my email from a Google Apps account. This allows me to have full, dependable offline access. It allows me to periodically backup and archive my mail, protection against the rare case where Google might somehow delete my mail on their servers. It allows me to have easy access to search mail back for half a decade."
Gmail's web access was down for a couple of hours the other day. A lot of domains are now having Google host their email. I'm thinking of moving one of my domains there to see how I like it. Aaron already has 2 of his domains there.
By accessing your gmail using an email program like Thunderbird, or Outlook you can always read your mail even if Google's mail is down. (The POP still worked, the last time Gmail went down.)