New, we were on the Disney Magic Nov. 2001 for a 7 day cruise. We are experienced cruisers (14) and I nor my wife have never gotten sea sick. My daughter got a bit queasy on the SS Independence in Hawaii in gale force winds and seas in 1994 but that was the only time. The Indy did not have stabalizers. The Magic is a beautiful ship with great kids entertainment and quite places for adults only. Also great entertainment and food. Every night they change which restaurant you eat in, though you sit with the same people and have the same wait staff, which was fun. Each Rest. has a different theme. I think they are still doing this your agent can fill you in about this also. Their specialty restaurant is called Palo's, don't miss this one. There is a extra charge for this but is well worth it. No kids were allowed in Palo when we were there. If you do decide to eat there make reservations when you first get on the ship and don't pick the same night you are suppose to eat at Animator's Palate you won't want to miss that one either.
On our cruise we hit some heavy weather a few times, but was hardly noticable, as with most newer ships that have stabalizers. My wife can't ride in the back seat of a car or towards the rear of a bus without feeling ill, but the water dosen't bother her at all. You will never know how you will react on a ship unless you try it. Hopefully you will be fine. Just relax and enjoy, sometimes I think "some" people worry to much about this. I know there are some that just can't take it.