This was my eighth Carnival cruise, taken solely to help me achieve Platinum status this summer. I talked 4-5 people who were on the boat for the same reason.
Positives - Blue Iguana Cantina (breakfast and lunch), Guy's Burger Joint, and the opposing bars on deck. Very cool setup that no other cruise line has. The burgers and burritos very good compared to typical buffet fare. The combination of these bars and eating places made for a very lively main deck. Boat was in really nice shape and the service was good, similar to others in the same class. Pizza was very pretty good to for "cruise ship pizza" (thin crust).
Negatives - Smoking rules not enforced all that well, charging for a behind the scenes tour on a cruise to nowhere, lido deck buffet somewhat bland and horrible lines at breakfast. I realize that space is limited, but this is something RCCL does much better by breaking up the foods by type/station.
This itinerary is only offered a handful of times a year so I'm not going to tell you about every detail. Just know that due to the very short length (and low cost) don't go on this boat looking for something to complain about. I know the stereotypes of the Carnival brand, and this crowd lived up to them. That being said, I had fun but would probably stick to 5 day minimum cruises going forward (couldn't do it this time as I have already scheduled all my available time off).