It's pretty cool do download an archive though, instead of going through IMAP, for archival purposes that is. I have a lot of email in my GMail, going back to 2005 I think. I'm afraid of accidentally deleting it, plus I also use other email clients, like Thunderbird and I'm always triple-checking settings to ensure it doesn't delete old emails. Having the option of doing a dump from time to time, for storage, is really cool.
Check out "offlineimap" (or similar utilities) that sync your Gmail to your local machine over IMAP. Run that via cron and can back up your mail like normal.