Julio's place is fantastic - right in the middle of town, on a street off Piazza Bellini, 5-10 minutes away from Napoli Sotterranea and all the shops, markets and restaurants - everything you could want. Although the space is located next to the Piazza the room faces the other direction so it is very quiet.
The apartment is very clean and kept to a high standard - Julio was always there if there were any problems and was very quick to solve any issues.
The only issue (although not a big one) was that the wifi wouldn't connect to the internet now and again, and we couldn't always get a phone signal (we're both with Vodaphone so it might just be them and not the flat itself).
But overall the apartment is excellent and Julio is a great host. Highly recommended!