I did the Atlantic crossing in April of this year on the Brillance from Miami to Barcelona. I did a tongue in cheek review (but reasonably accurate)on it and you can probably find it on search if you are so inclined.
However, the crossing was perfect. The temperature was 82 degrees every day and, while the seas ran about 6 feet, there was no movement on deck. You would have thought the sea was glassy.
Winds on occassion were 20+ miles an hour and had no impact (that I could see) on the waves. On the protected pool deck, there was virtually no wind and every deck chair was filled with sunbathers.
Never saw (or heard) of anybody experiencing sea sickness and people were always walking and jogging on the running track.
On just one day of the cruise, the water in the pool sloshed a bit, but not enough to drive anybody out of the pool.