We were on the Jewel trans-atlantic this past April and it was quite rough the first few days and the weather was bad all the way across, so there were no outside activities. Six days at sea can become quite long when your inside the whole time.
We would do it again though not the same route.
We did one on the Grand Princess. Just beautiful. No early calls for ports. Just relax and enjoy the day.
Ours was a Med to Galveston, so we saw about 6 ports before we began to cross. We stopped in the Bahama's so there was a break in the crossing.
SS Norway (12 times) '85 - '97; Radiance OS 06/01; Island Princess 11/04, Grand Princess 11/04/05, Golden Princess 7/21/06, Golden Princess 2/24/07, Explorer of the Seas 12/23/07, Island Princess 11/15/08
You can certainly hit rough seas but I think this is one of the last hidden treasures in cruising. The prices can go SO low on these crossings! Main thing is to be okay with the possibility of the motion and be the type that enjoys the ship's experience (vs. port intensive trips). We went on the Nav in April 07 and booked 09/08 for the Jewel crossing while onboard.