I found the reviews at Cruise Critic to be very helpful. I also think Costa must be reading the reviews as well because everything prior reviewers complained about has been improved or outright fixed.
First, the cabin. Our cabin was on the smoking side of the ship (odd cabin numbers, not even) and the prior occupant smoked up a storm, which I found disgusting. Upon boarding, the room spelled like smoke. Our cabin steward, Rocio, was very friendly and re-made the room with non-smoking linens and treated the air through the air-conditioning system to eliminate the smell. She also emptied our wet-bar, per our instructions, so we could fill it with items we brought with us. She did all of this before we even left port...and with a smile. She also brought us extra pillows and an extra blanket very quickly and with a smile.
The entertainment was very good.....especially DO NOT MISS seeing "Myth Trio". They are 3 people who can do anything Cirque de Soliel does, but on a moving ship. They were terrific!!!