I have travelled with my husband, we got a "premium cabin" thinking that the amount you pay more than a classic cabin, is worth the expense. We got a cabin right in front of the hot tubs engine room: a constant loud engine whining from 07.00 until 21.00hrs.
The cabin crew : spectacular, even if visibly reduced, they managed to clean and very well our cabin twice daily, finding also the time to make towel animals.
The restaurant crew : same as cabin, very kind and helpfull in everything. Still try to sell you bottled water when the normal one is perfectly ok.
No way to get a hot tea in a cup bigger than cappuccino size.
The spa crew : very kind and apologetic when the steam bath or sauna were out of order, pity no one checked if they worked when opening.
The pools : small, you stand in them and absolutely freezing, even the hot tubs were cold tubs. The roof of the covered one was left open when it was cold (the first day of sailing) because - this was the actual answer - it can not be closed while sailing. Pity that they had to close it the following days because they could not set out the sales tables, and we were sailing. And from there on it remained closed, we went through the "tropic passage" in a closed, cramped pool area. No way to see anything.
Service, in general, is gone down the hill at full speed.
The food : absolutely not in Costa standards,the cruise had been sold to large groups of french and german guests - apparently - at a very low cost.
Excursions : the only one we did with them (Tortola Virgin Gorda) was booked because we had been scared in the eventuality of loosing the boat. Not true : on the spot we discovered that other people were doing what we were doing for half the price.
If I ever cruise again with Costa, and I doubt it, I will only if I get a ridiculous price like the others. I will never again book well in advance.