The archive button actually moves mail from the inbox to All Mail rather than creating it's own Archive label. It took me quite a long time this morning to figure out what was going on with my mail and where it was moving to. In previous versions, hitting the Archive button in Mail would create a new label called Archive to move mail into, making the user have to drag mail into the All Mail folder from the inbox in order to archive it. Now, the All Mail folder serves (as it should) as the Mail app's archive folder. Finally.