We did Connie last May on the Transatlantic and was very happy with the ship. We had previously been on Summit and Connie didn't disappoint in any way. I think you will love the ship and the experience.
Have cruised Celebrity, RCI and Carnival and have found good in all of them. I am very much a Celebrity fan, but I like trying all the cruiselines. I was like you, very hesitant to go on a Carnival cruise but I would go on the Carnival Spirit class ships again in a heartbeat. Love the layout of the ships, the entertainment was very good as was the food and service. Try it you'll probably be very pleasantly surprised if you are at all like I was.
Enjoy Constellation and the warmth of the Southern Caribbean. After this winter everyone needs a cruise.