The old BAC 1-11 rear hold was a bit of a pig - very cramped and getting the bags to stay on the slope at the back could be a pain. Very noisy too if the
APU was running.
Next biggest pain, widebodies when the "automatics" aren't working down below.
Happiness is the "vent" on the VC10
146 nice and easy aswell due to low fuselage height - no conveyor needed.