I would definitely reccomend Valeria's place to a couple or solo traveller wanting to explore Naples. The location is great, just a few minutes from the sea front, bars, restaurants, castle etc. You can also easily walk to the town centre or to the port to catch a boat to Capri.
The flat is clean and relatively modern, it's small but it has everything you need. The air con is a unit in the hall, you can angle it into the bedroom or the living room but not both at once!
All in all a great place to stay and a beautiful city!