Overall, it's a very worthwhile place to stay with a lovely balcony view and excellent location, within 5mins of the main station. I'd highly recommend it if you intend to stay in Naples and do daytrips, but If you're here to see Naples itself there's likely a better location since its in a somewhat seedy (though endearing) part of town. My recommendation applies so long as the listed flaws are fixed, which are glaring sores on an otherwise lovely stay.
Pros: GREAT AIRCON
Neatly decorated
Great location and view of Versuvius
Host gave the BRILLIANT recommendation to see Castel Sant'Elmo.
Cons:
Clearly the apartment has been recently transformed from an otherwise neglected apartment block which is obvious from outside and when ascending the stairs. This isn't an issue in itself but in certain areas the renovation 'missed a spot'.
One toilet has no light and makes the sound of a train crash when flushed. The other squirts water from the tank.
The kettle has a leak which briefly took out the power from the apartment.
The beds were made up as doubles and there were no spare sheets to change them to singles.
And it's up five flights of stairs.