The problem, as Long Haul sees it, is that he gets all the work and very little of the excitement and the glory that goes with being a Decepticon. He knows his job is important; he'd just much rather be on the front lines fighting shoulder to shoulder with fellow warriors than moving supplies and building installations to make sure those warriors continue fighting. Long Haul keeps these secret desires to himself though, as he's smart enough to know Megatron is not likely to be sympathetic and has no patience for grunts who question their orders.
He also serves as Devastator's crotch. Tough break.
His alt-mode is a green Dump Truck.