Air conditioning in stateroom was awful, but at 72F-75F they will not adjust it. We got a fan which was noisy, drafty (got a sore throat from draft), and left no outlet to charge phone.
As you walk through ship you pass through distinct zones of smelly stale air.
The serving staff will not bring you a drink if they can't charge you for it. For example, they will not bring you a lemonade in the hot tub.
Carnival dropped Belize from the itinerary with no compensation. Belize was the whole reason I booked. The alternative, Costa Maya, is a shopping mall in the middle of nowhere.
Carnival provides no port information (maps etc.) unless it is for a paid excursion.
The whole week I felt like a captive audience with them trying to sell me more and more and more.
Shows were not as professional as on other lines (e.g. Norwegian). The magic show played ear-splitting loud music which many people I met complained about.
Buffets were OK.
Food in the dining room was excellent and the waiters were attentive and professional and got an extra tip from us. BTW Carnival's automatic tipping is supposed to be at your discretion but they limit when you can change it and the rules are different if you talk to the front desk vs. the customer service phone.
Cozumel was nice and the America's Cup yacht race is a great thrill. It is the actual yacht that won the race.
Isla Roatan was nice and renting floats to float on the lagoon was exquisite.
The virus struck 122 on our ship.
I won't take another Carnival cruise because they would not respond to my overly hot room. Norwegian has better attitude, better service, better shows, better bingo, and fresh air.