pros
Location is within a 20 minute walk to much of what you might want to see and do in Madrid.
Modern appliances and fixtures. Clean and well maintained. Luis provided a nice guide to his favorite restaurants and activities; ample supplies; and electrical adapters.
Good communication with Luis. Its clear that he wants to make your stay as enjoyable as possible. Responsive.

cons
No closet, few available drawers.
Noise from neighboring apartment.
Bathroom space is tight.
Our somewhat older phones and tablet were not able to detect the WiFi signal. Only place we had a problem in Spain.