Having just returned from RCI's Majesty of the Seas, I have a couple of tips:
Don't book deck 7 "ocean view" cabins. What you actually get is a view of the promenade deck and its pedestrian traffic (a friend of ours was sitting in his cabin and some guy pressed his face to the window looking in at him - kind of disconcerting!).
Keep in mind that the outer cabins on deck 6 are directly below the walking/running track of the promenade deck. Guests ARE asked not to run or powerwalk between 10pm and morning - and maybe they adhere to that, but you take your chances.
I also suspect that there are A LOT of obstructed cabins on decks 8 & 9 (there has to be - the lifeboats are up there). No firsthand on this though.
Oh, and despite reading to the contrary, there are not "safes in every cabin." We were in a deck 5 ocean view, and the only "safe" was the purser's desk. Maybe suites have them?
Great cruise though.