This apartment has the perfect location - only 10-15 min walk (or less) from so many of Madrid's top sites to see. (Plaza Mayor, the Prado, Malasana neighborhood, etc.)
We were very happy with cleanliness, amenities in apartment, communication with hosts - we asked for late checkout after a flight was delayed and it was no problem. Right now the main building door requires a key to get out so it was a bit tricky to leave upon checkout since we had left the keys in the apartment. Would suggest having one of your party hold the door downstairs and then run back up to leave the key in the apartment.
The front bedroom is the most picturesque but also lets in the most noise (garbage trucks, barking dog belonging to French restaurant downstairs, etc.). This bothered my friend but not her husband, so if you are sensitive to noise would advise taking one of the other bedrooms particularly the back bedroom in which we had 0 noise problems.