Mario, Antonio's son, really is a great host. He gave us a lot of awesome reccomendations for places and restaurants to visit. Most of them are pretty close to the apartment - 10 minutes walking.
About the apartment itself - it was clean and has everything you may need for a few days in Naples (including hairdryer - really important for the ladies). It's on the fifth floor and the building doesn't have an elevator so you'll have to use your muscles if you have a lot of luggage.
The second floor where the bed is has an AC and the temperature is great. The first floor where the sofa is may be a bit cold (we visited in February) but there is a radiator and probably it can help.
One slide door with a key separates the apartment from the one next to it. It's possible to hear some noise from the people in the other appartment if they are too noisy. But in our case the apartment was actually a little silent haven from the noisy and chaotic streets of the Historical Center.