Our group of 5 made a last-minute decision to book this cruise, and we grabbed what seemed to be one of the last 2 or 3 cabins available about 2 weeks before departure. A few days later, we then added another cabin for 2 grandparents who wanted to join as well.
I was shocked that our family of 5 (mom, dad, and kids ages 14, 11, and 7) would be able to fit in one cabin, but we did. We would have happily booked a second cabin if it were possible, but it wasn't; certain cabins are apparently designated for certain sized groups, even though I would later find out that all of the cabins (except for the suites) are essentially the same size. For example, there was a period of several days where we couldn't add the 2 grandparents because the only availability was a 5-person room, even though we told Carnival on the phone that we'd pay for 3 additional "phantom children" in that room if necessary (the kids were only $100 or $200 extra each). Luckily a 2-person room later opened up.
Embarkation was a breeze, however I was surprised that most of the employees at the port were not very friendly, except for the porters -- who were very nice. Maybe the other employees were tired by the time we arrived at 12:30pm from having to deal with another cruise's disembarkation that morning, followed by our cruise embarking in the afternoon - but whatever the case, it left me wondering what the level of service was going to be on the cruise. In the end, the embarkation process was very easy, and the crew on board ended up being exceptionally nice. Because we were taking a private tour in Havana led by a Cuban tour guide, we filled out our affidavits by choosing "People to People" under option 1, and then "Support of the Cuban People" under option 2.
Our cabin was able to sleep our entire family of 5. The two twins were pushed together to make a king bed for mom and dad. There were then 2 upper beds that folded down -- one perpendicular to the king bed at the foot of the bed, and the other perpendicular to the king bed at the head of the bed (i.e., literally over mom and dad's heads and upper torsos, so be careful not to bump your head when you sit up in bed). The fifth bed laid on the floor at the foot of the king bed (essentially under one of the upper fold-down beds). With all those beds, there was really no way to walk around the king bed without stepping on people, and the kid in the upper bed above the king headboard had to step on the king bed to get up and down; the other fold-down bed (at the foot of the king bed) had a ladder to use.
We were very glad to have brought our own clock (great tip I found online!), but the small portable fan was unnecessary. The over-the-door hanger for toiletries, etc. was another great tip.
The cabin was tight, but adequate. 5 hard shell carry-on suitcases plus 2 collapsible duffle bags fit just fine under the bed and were used as hampers for dirty clothes as the cruise went along. The bathroom size was fine. Water pressure and temperature were great. The closets and drawers were just big enough to hold our clothes. We made sure to keep everything tidy the whole time, given the small space, and the stateroom attendant was fabulous. There was a hairdryer in the room, as well as USB, 110V, and 220V outlets. Shampoo and body wash (both in refillable pump containers hanging on the wall, not individual bottles) were in the shower, but we were glad we brought our own bar soap. Some in our group thought the shampoo was lousy, so maybe we would have brought our own had we known. Had no issues hearing other guests through the walls (only once or twice did we hear kids running up and down the halls). Obviously no place to really sit down in the room, with the bed configuration that limited the ability to even sit on the bed.
We did a private tour with a Cuban tour guide (i.e., not an official shore excursion through Carnival). We absolutely loved our time in Havana.
Embarkation was very smooth. Disembarkation seemed unnecessarily chaotic (i.e., lots of waiting around).
We were on the fence about whether to get off the ship in Cozumel; when we arrived, the foreboding skies made our decision easy. We got off the ship to eat lunch at Three Amigos, then walked around the port for a bit before getting back on the ship; we had the entire ship to ourselves for several hours and really enjoyed ourselves.