The military stuff is bad, but the bin hauling gets my vote, because it affects everything!
All my working class gets interrupted all the time, because some stupid dwarf carries all the necessary stuff around in a bin. Jewellers cannot find their gems, farmers have no seeds, trade stuff is nowhere to be found when a caravan arrives, etc. Extremely annoying!
This.
I voted already, pointing at the hospital bug, after another legendary warrior died on the doorstep of my hospital, because he had a slight wound in the left foot, and nobody cared to help him. His buddy, recruit Urist McGreen, who was severely wounded and unconscious, was immediately carried to the hospital, and is still alive. If you can talk, you can walk, seems to be the dwarven logic.
But this bin-cirkus is really a pain. Not only in the day-to-day collection of stuff, as mentioned by others.
My dwarves dealt succesfully with a double ambush, and as soon as I lifted the civilian alert, literally everybody grabbed a bin and went outside to collect socks. Then a human caravan announced its arrival, and two seconds later: An evil Force of Darkness. I put my fortress back on alert and everyone took refuge inside, except my soldiers, who went outside to protect the caravan. I managed to get the caravan and soldiers inside my fort and seal it, just to find out, that I had no finished goods to trade with. All my bins (except perhaps four or five) and their content is littered all over the place - OUTSIDE.
I find it hard to decide which of these two bugs are the most annoying. I think that perhaps each user should be allowed two or three votes?