My wife and just returned from a cruise on the Costa Fortuna to the Greek Islands. Overall it was an enjoyable cruise. The ship is clean and our cabin was very nice. The stewards were excellent and pleasant. It was definitely worth the price.
Costa Fortuna could cost a fortuna. The excursions were so ridiculously overpriced that we skipped all of them on principle. We learned on the excursion to Bari, which is marginally worth seeing, that the ship was pushing organized excursions as a major cost center. Paying essentially $100 per person for a bus ride was, well, let's say, overpriced. Walking around the old city for free cost nothing.
Olympia really proved the point. The ship was docked for about 6 hours to allow passengers to get from the port to Olympia, about 30 km away. Those who took the ship-arranged buses, paid around $120 per person. My wife and I paid, round trip on the very convenient train, $4 per person. Some markup.
This occurred over and again. The staff pushed all sorts of exaggerated mark-ups, like wine, drinks, massages, etc. While many of these are justified and deserve a premium, the basic message came across: if you want to do anything, drink wine (which was confiscated if you brought it from the towns we visited), buy anything, expect to pay a high price. This alone irritated me to the point of not considering Costa again.
The shows were mediocre compared to other lines. The acrobats and dancers were excellent, but the crew put on a talen show and it was somewhat like watching a local high school talent show.
The food was pretty good, although I didn't really try to stuff myself like so many seemed to want to do. The gym was good and the saunas were convenient. The layout of the ship was odd, however, and getting to restaurants wasn't very easy.
Having taken a Celebrity cruise to Alaska on the Summit, I would have to say that the Summit was far better in nearly all respects. However, the Costa cruise to Greece was fun and we really enjoy Italy and Italians.