Very clean, tastefully furnished and pleasant to be in. Rosella is very knowledgeable about tourist attractions, letting us know that which things to book in advance.
We could hear the neighbors a couple of times in the morning, but not at night. We visited in December, it was quite cold, but Rosella provided an electric heater. I will say that there was not a lot of space for us to put our things - not a problem, but just to be aware that it is rather like a small hotel room. The room is in the 5th floor, with a small lift. There is a small kitchen with some crackers and coffee and a gas stove, and a small fridge.
The apartment is located inside the Spanish quarter, so quite atmospheric. Also nearby are the Napoli underground tours.