What annoys me etiquette-wise is when you end up in the closest bay to the scanner and everyone to the right (or left depending what side you're on) shoves their trays out before you can get yours. I've been left standing there while 2 or 3 people change over before I can actually get my tray out. Once after I got fed up I just shoved it forward and the guy next to me tried to tell me off. I told him I'd been there since 2 people before him trying to get the tray out.
To add to that 90% of persons then leave their tray on the system rather than picking it up and placing on the stack at the end after they have finished with it. Every time I go through T5 fast track I end up collecting about 5 trays and placing them in the stack.......... and suddenly the conveyor starts moving, it's hardly magic
It really irks me that many people going through fast track feel it's beneath them to remove their own tray.
Rant over