We were on holiday in Madrid and spent 4 nights at Maribel & Jose' apartment. The apartment is spacious, clean and quiet as it faces an inner patio. The location is convenient with many areas of interest at walking distance.
The entire building seems to be holiday rental flats. We did self check-in/out and had no issues at all. We also made use of the laundry room in the building and it was quite practical.
The only improvement I would suggest is to replace the sliding doors of the shower. They were a bit difficult to open/close.