Archive should provide visual feedback
Trying the new UI, I was trying to figure out how to hide (but not delete) completed tasks. I clicked the Archive button out of curiosity. Now I've lost an entire list of my tasks, with absolutely no indication of how to get it back.
Deleting user data with no confirmation and no undo really, really, REALLY bad. Please don't ever do this.
I'm going to go do filesystem surgery now to see if I can get my tasks back.