We just returned from a 7-night Western Mediterranean cruise on the Costa Serena. As some other contributors have mentioned, we were very apprehensive after reading all the negative reviews of the ship on this site. We really wonder what ship these other passengers were on, as we saw none of the activities mentioned by those negative reviewers.
First of all, it is true that only about 10% of the passengers speak English, but every member of the crew speaks English well enough to converse with you satisfactorily. Also, there are very few Americans on the ship, but it is an Italian ship - that is to be expected. We knew we were not sailing on an American ship!
The ship looks like a floating Las Vegas. Yes, it is brightly decorated, and it could be considered a bit "over the top". But, every place on the ship is perfectly clean and excellently maintained. There were some children on the ship, and they were very well-behaved or quickly disciplined by their parents. Also, we saw some smokers, but only when we happened to venture outside to the decks where smoking was permitted. There were many French, Italians, and Spaniards having a wonderful holiday and making merry on the ship, but they were never anywhere near our cabin. We only experienced peace and quiet when we went to our cabin for the evening.