Costa cruises are only worth considering if you can buy one really cheaply and forget any notion that you'll get good service and be treated like a guest. On the positive side the dinner service and food was quite reasonable, unfortunately everything else is very sub standard. The impression is that the company is struggling to make a profit and therefore is charging extra for everything it can get away with and reducing staffing levels to such a point that you simply have to wait for ages to get a drink or food. We've been on 4 cruises with them in the last 5 years and each time the experience has been worse. For example this time the following stands out (only a selection from many poor experiences)
Very, very slow service at breakfast, typically 40 minutes at least from placing an order (once you've had your order taken which again can be very slow) - on days where there are early excursions lots of people were walking out without hot food as they otherwise would have missed their departure.
Very few waiters and very hard to get a coffee or tea and subsequent top up at breakfast.