The general impression on Carnival Victory was that their ONLY purpose was to suck as much money from you as possible. 90% of the announcement were related to shopping, duty free, casino, photo services, bingo or something else that you have to pay for. On Costa they want to make money as well but not like this. Every service not included in the cruise price was ridiculously overpriced. For a 8x10 photo they asked $22. A simple 3-4 hours excursion on bus was $60-70 per person (not to mention special activities like snorkeling which could easily reach $100-120).
The embarkment was good, quick and efficient. The cabin was decent size, clean and nice. Our cabin stuart did a good job. However, our cabin was making funny noises (kind of squeaking) which was very annoying at nights. When we complained, they offered us ear plugs..
The staff was friendly and helpful. The service was okay, except for those waiters everywhere asking you every 2 minutes if you want to drink something (for a nominal price of $6-7). This was very annoying, but I guess it's their policy on every ship, not only Carnival.
The food was below average on breakfast and lunch (no vegetables in the morning!). Dinner in the formal seating dining room was just okay, much less than we expected. The main courses arrived cold at least 2-3 times. The variety was quite limited in both dining rooms, the lines on the buffet were huge and some of the food was recycled day after day (for example, on dinner they had ceasar salad all 7 nights).
The entertainment was another big disappointment along with the food. The main evening shows were good, but the rest of activities quite limited and boring. The cruise director Malcolm was great, but we hardly saw him and the rest of the entertainment team. On Costa, we had no single boring moment. On Carnival, they had bingo every night (to make few more bucks for Carnival), few trivias, couple games - that's it. No aerobics, no pool activities (maybe one or two). The afternoon tea and classic music - only 3 times, compared to every day on Costa.
Please notice that if you travel with teenagers, there is a Carnival camp for them, but if you want to spend time together after 10pm, the options are very limited. Teens under 18 are not allowed to any club after 10pm. They had an eighties party one of the evenings, but we couldn't attend because they ask an ID from our daughter. That's just ridiculous. Never happened on Costa.
The disembarkment was okay.
Summary: Cruise by definition cannot be a bad thing. It was a vacation, so we had a great time despite all those small things. However, for the similar price, Costa Mediterrania is in a different league. Carnival staff did their job okay - no more, no less. Costa went few steps beyond.