We had a nice stay at "Il cinquecento".
The location is pretty central close to the duomo and the via tribunali, The room and the bathroom were clean and sheets were provided.
But there are also some downsides:
At the arranged time, there was nobody to pick us up or hand us the key. We finally had to call the Airbnb helpline. They were able to contact the hosts dad who then finally sent someone with the keys. Furthermore the TV wasn't working and the room was quiet noisy as you hear all the voices and steps from the second guest room upstairs.
All this didn't really bother us (One usually doesn't go to Naples for silence and efficient organization..) and we enjoyed our stay very much.