I am an avid cruiser and I had sailed on virtually all major cruse lines including Costa before I took my Dec29-Jan8 Caribbean cruise on Costa Atlantica.
The good: like all other cruise lines, Costa follows its itinerary, the rooms/bars/restaurants/shows are OK compared to the other mainstream cruise lines.
The bad: they have been absolutely disorganized, careless about customers and have messed up things we could have not even imagined.
Below are only the facts from my real experience:
1. Booking. We couldn't book Costa cruise on the weekend. Their computers were rejecting all reservations and their agents didn't work during the weekend. This issue was confirmed by travel agencies and fellow passengers on the ship. Good side: my room was still available on Monday, as they nobody could buy it over the weekend.
2. Embarkation. They didn't properly process our documents and on the way back the officer at the border couldn't see that we had ever left USA for the cruise. Not a big deal for me but it could have created immigration problems for those on visitors visas.
3. Missing room credit. Our cruise was sold with the $100 room credit but on the ship they just said that "our computers don't see the credit". I spent 7 days in a row talking and escalating and every day the response was "come back tomorrow". After 7 days, they finally admitted: we cannot solve it, essentially meaning "we have stolen your money, go to hell".
4. Internet service - they may mislead you and steal your time. To disconnect, they said to type "logout.wifi" from any browser. So we did, and got confirmation "You've been logged out" But our internet time still disappeared. Through trial and error we found a way: after typing "logout.wifi" there's one more "logout" button to click which they never told us about. After clicking there I got a message "you have been properly (!!!) logged out. The counter has been stopped". They never advertise this as the way to PROPERLY log out.
5. Finally, their port service. I was unfortunate to forget some items in the stateroom after I disembarked on Sunday. I already knew that Costa doesn't work on the weekends, but in the daily bruchure they posted a telephone of their Miami port agent "for emergencies" while on shore. So I called that number and discovered that they were all out for the weekend. Nice EMERGENCY service, thank you Costa!
Thank you for the time spent reading this long review, I hope it would be helpful for future travellers.