Now the first problem, not the big problem, just the first one, is that you can't just select a folder and say you want to archive anything in it. Instead i have to check the "check all the boxes checkbox," and then i have to click on the "More" button and select "archive" from the drop-down. Then i have to click the check everything checkbox again to unselect everything, then go to the next page in that folder and do it all over again. This can take awhile. I could probably adjust the settings somewhere to increase the page size from 50 to 100 or more which would speed it up a fair bit, but it's still kind of dumb.
However what's _really_ bad is that when you first open a folder/go to a label there are three buttons at the top. The check everything checkbox, the refresh button, and the More button. However if you don't have anything checked the More button only has "Mark all as read" in the drop-down options. (This would be the perfect place to put "Archive All" so we could skip several steps.) But when you mark any emails as checked, either individually or with the all at once button, the buttons expand to make room for new options. However there's often a slight delay, especially if you're doing lots of actions in a row. Which means if you go into autopilot mode and it's being especially laggy you can click the "check all" button, then before it manages to refresh move the mouse over to the More button, and click right as it slides over to the right, leaving either the "Spam" button or the "Delete" button under your mouse.
I just marked 50 important emails as spam because Google's UI sucks. Of course i was able to go into the spam folder and unspam them, but i sure hope Google's algorithms know to ignore the "input" if a bunch of emails are marked as spam and then immediately unmarked.