The apartment is quite spacious and perfect for a group of four people. The bathroom is quite small and you have to wait your turn but it's not like you'll be in the apartment a lot.
The location is perfect - right across Piazza Dante and the metro station, and only a street away from the vibrant Piazza Bellini (the Old Town). It's a walking distance (30 minutes tops) from all the major areas you'll want to visit.
Me and my party had a small train delay and ended up checking in a bit late (around 9 pm). The host was super nice and patient with us (note that there's a 20 EUR deposit if you arrive after 8 pm). He welcomed us in front of the building and gave us a detailed map of Naples and useful tips and recommendations. We'd definitely come back for another visit :))