I cruised once on the Carnival Glory. It was a 7-Day Eastern Caribbean (Nassau,St.Thomas,St.Martin) cruise. It was back in Dec. 2006. I had a great time and it was always smooth through-out the entire cruise.
I am not sure whether the Glory had excellent stabilizers or whether the seas were light and smooth.
The most movement I expierienced on any of my five cruises was onboard the Norwegian Pearl last December. It was the evening after we left Cozumel. It was difficult to walk a straight line through the passageways (hallways) (maybe unless you were drunk
). I do remember the crew leaving those familar paper motion sickness bags near the elevators. The swimming pool on the Lido deck looked like the scene in the Disney movie Fantasia when Mickey was conducting the orchestra. But despite all that, it wasn't too bad. I asked the crew if they were ever in worse seas, and they said they have been in "much worse".
I guess, whether or not the ships movement is rough depends on how rough the seas are. The stabilizers can only help so much. But now-a-days the ships are bigger, so that helps too. However, one should hope for smooth seas at the time of their cruise.