I love the archive button, but what would make it even more useful is if there was a dropdown list box beside it that allowed me to pick which archive folder to use. I actually archive mail in multiple folders, such as one for people, one for interactions I have with companies, etc.
Sometimes when I’m monitoring a particular mailing list, I let all of the mail land in my inbox on the IMAP server and then I need a convenient way to file that into the mailing list folder. So, having a programmable list of folder options would make it easy to archive messages into whatever folder I select.