This is a nice apartment. We were five friends on a budget and their was plenty of space for all of us. The building that it's part of is gorgeous, the neighbourhood is very busy and noisy, but we didn't have noise problems inside the apartment.
I didn't meet Celesta herself, but he mother was friendly and helpful.
Note to people who have a car (and nerves of steel - Napoli driving is not for beginners) - there is a secure garage nearby, but it could be useful to book it, as we found it full and had to talk ourselves into getting a space.