I just took a 7 night Disney Cruise right before Christmas. We went on their Fantasy ship down to the Virgin Islands, San Juan, and Castaway Cay in the Bahamas. Like mentioned earlier, Disney ain't just for kids and everything they do is first class.
They have a Northern Europe cruise and a Hawaii cruise coming up this year that would be awesome to go on. I've never been on a Carnival Cruise, but they had one parked next to us in Canaveral and it seemed like a big party. Probably wouldn't be my thing, but to each his own. From a distance it looked more like a singles cruise atmosphere than a family type vacation.