If you are talking about on line check in, it won't hurt so no reason not to. You can put, I think, up to two preferences for your room. They are not guaranteed. Rooms are assigned 2 or 3 days before arrival but if you get to one and don't like it for whatever reason you can ask to be moved, they may or may not be able to do so. Some people get messages before they arrive with the room numbers and can actually just go straight to their rooms, never happened for me. There is normally a special desk at check in for on line check in that should, in theory, take less time since they already have your info. I do it and still go to the front desk just because I like the human interaction and I can't ever remember my pin number for my magic band and have to reset it every time.