My wife and I sailed on the Navigator last year. Although we weren't on as high a deck as you will be (we were on deck 6 forward/starboard), we never experienced any discomfort or even noticed that the ship was moving. Granted, our weather was almost perfect, and not everyone feels the effects of ship movement. Being our first cruise, we were concerned, but I guess we're some of the lucky ones.
The ship is fantastic. We had the best time of our lives and celebrated our 30th anniversary. The staff and crew could not seem to do enough for us. I definately recommend the ship.
Have a great cruise.....