Santolo was very friendly and communicative. He responded to my messages quickly and thoroughly. On arrival he greeted us warmly and bought us some groceries in advance as we arrived later on in the evening. He had prepared some recommendations for attractions, local amenities and timetables for buses etc.
The apartment itself is a studio apartment but has all of the essentials and we only really slept there as we obviously spent a lot of time exploring the city and surrounding areas. It is also well situated - a twenty minute walk or so to Napoli Centrale train station, plenty of shops and not far from the Universita metro station. The only issue we had was that with the apartment being on the small side and not having any ventilation other than a window above the door and an extractor fan in the bathroom the moisture built up in the air and smelled damp upon arrival in the evening. You could also see on the walls and ceiling where the flat had suffered from damp previously. One other thing to note is that the apartment is right on the street and is therefore a little noisy, though you should be fine with earplugs or if you're a heavy sleeper!
All in all, for the price, location and friendliness and generosity of Santolo I would recommend his apartment.