We stayed at Ariel's for 3 nights. He was very nice and understanding even if had to change our arrival time a couple of times the day before but we could arrange everyting without problems by messages.
The flat is right in front of the Metro station and close to all the main turistic attractions: we practicly walked everywhere.
The room was right as in the photos, very nice and clean as also the kitchen and the bathroom.
Ariel himself was very nice and friendly and gave us some nice tips for Madrid.