We had a great stay in Alessandra's appartment. We were nine women and the appartment was certainly big enough to fit us all. It's located in the city centre, which was perfect for us, but you need to take this into consideration if you do not like the noise of the busy city life. We did have some problems showering all at the same time, but of course like Alessandra said, it's not a hotel.
Our contact with Alessandra was perfect, no problems checking in or out, she was very flexible and forthcoming. She had a lot of information and tips for us as well.
I would certainly recommend staying here if you want to spend a weekend in Naples.