Location
Mario's place is an excellent headquarters for exploring Naples and the region around it. It is well connected to the city having both the metro, train and bus terminal at no more than a 5 minute walk (through the Galleria on Corso Meridionale), and a supermarket at less than 300m.
Apartment
It rests exactly as the pictures show it to be, a really spacious, clean apartment, ideal for a family or a group of friends, having all the amenities necessary (iron, kitchen utensils etc.). The bedrooms are very big with plenty of storage space, which makes organisation really easy. The only negative point I could see to the apartment is that the bedroom windows are not very soundproof and in some nights street noise can become a problem, but it hasn't always been the case.
Host
The communication with the host was as the other reviews mention, smooth and very efficient. They accommodated for an early check-in and an even earlier check-out without any problem, which has been very helpful. Overall our trip to Naples was made perfect with the help of Mario and Fabrizia.