I've been aft on both of my cruises. The first time because there was no other option (needed a handicapped access room), but chose it second time because (1) I'd read on these boards that stairs/elevators were less crowded there and (2) like stated above, it's so convenient to Topsiders, soda machine, Mickey Pool, Animator's Palate, Parrot Cay. Especially if you're on deck 6 or so, it's only 2 or 3 flights up or down to anything, and definitely faster than the elevator.
As far as movement, I can't compare since I haven't stayed in other areas, but it never bothered me a bit; in fact I found it soothing, but am not sensitive to motion as others might be.