Hi bklawyer, and welcome to cruise-chat.
We had cabin 728 on very-near-sister ship Maasdam, which is midships on A-deck. Ride was very smooth, and once our cabin door was closed, we heard very little from the hallways or adjacent cabins. We did, however, have some vibrations when pulling into or out of port, but it didn't last long.
HAL's outside cabins are better than most, IMO. We had a bathtub, for instance. The cabin was quite spacious -- and there were three of us.