Overview -- The Christmas cruise was fully booked. There seemed to be an incredible number of (usually crying) babies and toddlers, and quite a few grade-school age kids, but very few teenagers. Since this was a holiday cruise, big families were the order of the day. I didn't see any of the rowdy partying that Carnival has a reputation for.
Carnival calls themselves "fun ships" rather than "elegant ships" for a reason. The cruise had a Saturday-at-the-mall feeling. With some 2,000 passengers on board, the ship was *crowded.* Everywhere you went there was a line, especially if food was involved. The photo gallery was a zoo, particularly after the "formal night" pictures were posted. The elevators were frequently packed, especially at peak times such as after dinner.
Embarkation -- Getting on the ship was a breeze, even with heightened security procedures. We stayed on the Queen Mary the night before, something I highly recommend. There is a special early boarding for Queen Mary passengers, and it was very worth it. Our luggage appeared at our stateroom door very quickly, within a couple of hours. Not bad at all.