Me and my partner have cruised once before, a few years ago. We liked it so much that we decided to try it again for our vacation this year. She teaches at a university, so the week of spring break was our only option. We got a fantastically cheap deal; even with airfare from LA it was the cheapest exotic international vacation option we could find.
The ship is in fine shape, don't let the reviews about it being old scare you. It is well maintained and recently refurbished, and you have to look hard to see any imperfections. It is midsize, which was actually quite nice; it didn't take too long to get anywhere on the ship, but there was still plenty to do, including a casino with poker, library, cigar room, water slide, spa, exercise room, six hot tubs, many restaurants, and constant entertainment and games.
The dining was fantastic; much better than the previous Carnival cruise we went on. Every night we ordered 3 appetizers and 3 desserts each, then went to the buffet for more afterwards. Not every dish was amazing, but most were. We only paid for one premium dinner, at Le Bistro, the french restaurant, and it was well worth it. The lobster was truly delicious. We were so satisfied with the regular dining the rest of the nights we felt no need to spend more on premium dining.
We got the cheapest possible cabin, so we knew it would be small. It was big enough for two of us. On the 8th floor we could hear some activity from the Fyzz Lounge below us if we tried to sleep early, but not too bad. The painting in our room rattled as the ship vibrated, so loudly we called and had it removed. Overall the cabin was just fine, and for the price it was all we could ask for. Protip: the decorative fish on the hallway floors swim towards the front of the ship.
We had a late flight back and spend the day at the Natural Science Museum - it was one of the best museums we've ever been to. If you have the time to spare, this beats the space center by far (and I am a PhD holding science nerd who loves space).