Other than one small glitch with communication when a cell phone didn't work, and which airbnb quickly corrected, the stay was very pleasant. Alberto searched us down when the taxi driver dropped us on the wrong street. The apartment is one flight up from the street, small, but bright, well equipped, very clean, comfortable and quiet. Alberto was readily accessible, although we didn't need his help once we found the apartment. The location is great - very close to Plaza Mayor.
Nothing to do with the apartment, but do not take a taxi to the airport. It cost us 50 euro - 33 euro on the meter and a surcharge. The train and the Metro both go to the airport from the nearby Sol Metro stop for about 5 euro.