I have a few suggestions that would make things a lot easier to do.
First off, there needs to be quick access to archiving an e-mail. Either have an archive button in the toolbar or one in the right-click menu. Having to open each e-mail to archive it is time consuming.
Second, there should be a way to select multiple e-mails and hitting the archive button to archive all of them. A good example of this is used in Thunderbird.
Finally, archiving e-mails should be supported for non-Gmail accounts. It would be much simpler to hit the archive button and send the e-mail to the ‘archives’ folder instead of manually moving it there by browsing to the location.