Location-wise Gianmaria's flat is located in the heart of Naples, just 3 minutes walk from Michele's Pizzaria (which is a good thing, but also a bad thing as you'll be eating Michele's pizza for every meal, it is so delicious!). That said, you'll be burning all the calories from the pizza as you climb c.100 stairs to reach the flat. The advantage of being in the top floor is that you have a lot of natural light coming into the flat from the balcony door.
The flat itself was very nice. You will be staying within Gianmaria's flat, but you will have your own space which includes its own bathroom and kitchen. The door to your room will be situated right next to the main entrance door, therefore it doesn't really feel like you get into somebody else's house.
Gianmaria was an awesome host. Communication was really easy. He was very accommodating with regards to check-in and check-out. He also helped us book our taxi to the airport, which was waiting for us just outside the building door, and was a cheap ride of c.20 euros to the airport.
All and all we had a great experience and I recommend this place to anyone.