Positive thing: the cabin area and layout was good.The old style shower curtain was a challenge. After one took a shower the bathroom was like a swimming pool.I felt sorry for the cabin attendants.
The food was a disgrace. The self service for breakfast and lunch was very limited in options and without any alternatives for a passenger who wants to do a balanced diet. As an example, no skim milk available and one had a choice of butter or ... butter. Toast only of white bread. The food was tasteless and presented in a way that reminded me of my days at the university canteen. Surprisingly enough the self service was not open for dinner (remark out of curiosity since that would not be a real option). The only reasonable service was the "tea service" at 4.00 pm.
In what concerns the service in the dinning room I have never seen anything like that. The attitude of the waiter and assistant waiter was terrible (since the gratuities are standard they do not care about the passenger opinion). During the whole cruise never saw the Maitre D. No light options in the menu either for main courses or desert. The presentation and quality of the food was by far the worst we have experienced in all the cruises we have sailed (Royal Caribbean, Princess, Celebrity, Holland America and even Carnival).
We were so disappointed that we went on the second night to the "Special Restaurant" where a fee of 25 Euros per person applies. What a disaster! Worst that in the main dining room of the other Cruise lines we sailed with. From the starter to the desert it was a gallery of bad cooking and terrible presentation.
Unfortunately this proved not to be an alternative to other nights. So we returned to the main dining room where we enjoyed the company of our fellow passengers from Spain and Argentina (by the way our experienced cruise fellows from Argentina were on this cruise as a compensation for a very bad experience with Costa before and shared our opinion - Costa never again).
Regarding entertainment there were some reasonable options across the ship for dancing and the disco had a good atmosphere. The shows in the theater were ridiculously bad and weak with the exception of the "Celebration" show with the dancers. There was no orchestra (!!!) so all the music was recorded. They had a magician and a circus performer that were pathetic and could not get any reaction from the audience and one night the total show was performed by members of the crew. I had never seen anything like that. The Cruise Director was totally ineffective and provided no drive or enthusiasm among the passengers. The Staff tried to generate some excitement throughout the ship and they were effective in that task.
The fact that the ship takes passengers in all the ports results in having every day a long (in 6 different languages) safety and administrative announcements through the speaker system. It is a torture every afternoon. Fortunately and after a series of complains, the sound was eliminated from the cabins. When those announcements occurred one had to run to the balcony (no volume adjustment was available in the cabin).
Last comment relates to the very limited ability for the staff to speak and understand English. With a few exceptions most of the staff throughout the ship and even some staff in the Reception had significant difficulties with the English language.
In conclusion, if you are used to the normal standard of the "American" Companies stay away from Costa. They are not expensive in absolute terms but provide very little value for money. As I normally say, I had "two cruises in one" - the first and the last. Costa never again!