My wife talked me into buying a 7-day cruise from New Orleans to Jamaica/Grand Cayman/Cozumel. We went there with our two kids, aged 5 and 6. This was my second cruise (the previous one was a shorter, 3-day in Southern California) and quite possibly the last, at least until I can afford to pay more for a more decent experience (with tips and onboard spending, but not including the cost of getting to/from New Orleans, this trip came out to about $3000 for the four of us).
Generally, good food. Decent variety of items at the buffet for breakfast and lunch. I liked the salad bar. Even with all those unlimited desserts, I managed not to gain too much weight because of it. Dinners were delicious. Extra point for Indian vegetarian entrees. There was a sushi bar (which I, unfortunately, did not get a chance to try because it was closed or selling teddy bears most of the time.)
Entertainment. In the evenings, there was something interesting going on most of the time, shows, concerts, competitions, etc.
Camp Carnival. Nice place for kids to play with each other to keep them from getting bored.
Fitness center. This one gets points simply because it's there. It didn't seem to be very popular (it was half-empty on all three occasions I've been there -- I would've gone more often but I was sick the rest of the trip, see below.)
The place was fairly unsanitary. It was regularly cleaned, but the crew didn't seem to put much effort into it. For example, tables in the buffet room were cleaned without bleach or disinfectant. Given that the ship was packed like a sardine can, the potential for epidemics was huge. After the cruise, they were in such a hurry that lunch for new guests was already being set up as the last people from the previous cruise were leaving the buffet room to disembark. There simply wasn't much time to clean the ship between groups. Personally, I've managed to catch a cold not once, but TWICE during the trip, and my entire family got sick too.
I can't help but wonder if the attitude towards cleaning was in part due to the composition of the crew. Among those who were doing cooking, cleaning, etc, most were from third-world countries like Philippines or Indonesia, and those that weren't, were from Eastern Europe. I think I saw a total of one person from the UK and one from South Africa.
The room was tiny. Obviously, I had to foresee some hardships when booking one room for 4 people, but it was even more cramped than I expected. Shame on Carnival for allowing this layout. There were two twin-size beds on the floor, moved next to each other, and two bunk beds hanging off the walls. Which wouldn't be too bad if the room had a healthy ceiling height. If I'm not mistaken, all rooms on most decks have 7 foot ceilings. Even a fairly short adult can't walk under the bunk bed without crouching over. I have a painful bump on my head from hitting the edge of a bunk bed on day 2 when I was getting out of bed in the morning.
There was a single air conditioning vent in the center of the ceiling, which wasn't adjustable from within the cabin and was permanently blowing cold air. (We had a dummy thermostat on the wall that wasn't doing anything).
Nickel-and-diming. I understand that the cruise ship has limited satellite bandwidth, but seriously, $0.75/minute for internet access? At least have the decency to charge by megabyte. Outrageous prices for onboard alcohol. (But I'm given to understand that that is the norm rather than the exception.) By day 4 I was able to discover (completely by accident) that there was a single place on the ship where I could buy half-decent beer for $15.50 + 15% tip for a 60 oz pitcher. Which is still at least twice the price I'd pay for comparable beer onshore, but at least it's tolerable. Even the duty-free gift shop, which was advertising prices 20-50% off US retail, was really selling hard liquor at prices that were usually comparable or higher than what I can find locally. (Here's a random example. The gift shop was offering Johnnie Walker Black Label for $36/liter, "34% off retail". Our local BevMo sells it for $26/0.75 l + 7.75% state tax.) And you can't drink alcohol you buy from the duty-free shop, they keep it till the evening before debarkation.
Speaking of debarkation. They sent us a detailed schedule, predicting debarkation times by deck and by zone, down to minutes (if I remember correctly, we were supposed to leave the ship between 9:55 and 10:05), and then managed to blow it by an hour. I actually set foot on the gangway at 10:44. Then there was a loooooong line to get through customs, with 3 or 4 customs officers trying to process 3000 passengers.
Overall, I got the impression that late May is way too late for a Caribbean vacation. It was very hot and humid (in the 90's during the day) and I was hiding in air-conditioned parts of the ship most of the time. I didn't go on any excursions, I was either too sick or too cheap to pay $50+/person, but I made sure to get off the ship and to walk around in each port.
Montego Bay, Jamaica: a few cleaned-up touristy locations, interspersed by slums. The city could really use a new coat of paint and some cleaning. Perhaps if they took all the idle people from the streets and put them to use collecting trash or painting walls, it would soon look much nicer. I wouldn't risk being there after darkness.
Grand Cayman: very nice-looking island, even off the tourist route. (From what I read, also very expensive, even by U.S. standards.) What do they have against sidewalks? I walked from the pier to Sunset House Hotel and back, and I had to walk on the road most of the way.
In terms of shabbiness, halfway in between Montego Bay and Grand Cayman. This is clearly Mexico, but it does not feel as dangerous or dilapidated as Jamaica. I didn't have time to get out of town, but I could see myself coming there for a few days, swimming and exploring the island.