Exchange cabin bag for priority boarding
Did this last night on the way back to BFS from LTN. I have to say it is a good idea - got a over-wing window seat in exchange for a 5 minute wait in BFS on the case. I did it mainly to get away from a group of 50 excitable schoolkids who were in the queue behind me!
I have had this before with hand luggage on CRJ's where they can't fit the bigger roller bags into the overhead bins. With Lufthansa they tag it and you leave it at the bottom of the A/C steps and collect it there at the other end.