We stayed at Francesco's place for a month. The place is amazing, exactly as described in the website. The apartment is big, airy and spacious, with 3 balconies, fully equipped kitchen, and an air conditioner in every room. You can find there everything, from a dictionary, cheese grater and pen and paper, to a nut cracker, and lots of pots and pans.
The location is great: very close to 2 Metro stations, right near the beautiful Vomero neighborhood, few streets away from a big open-air market. Every second Sunday there is a farmers' market at the piazza under the apartment, with great selection of local cheeses, fruits and vegetables. There are 4 coffee bars under the apartment, where you can also watch soccer games when Napoli plays. The neighborhood is vibrant, with 2 great pizzerias, at least 3 supermarkets, Salumeria, fish stores, butcher, fruits and vegetables store, deli, etc.
We loved Napoli, and it was great to come back to the apartment after a busy day of touring this lovely city. We recommend this place with all our hearts.