The appartment is well located, super accessible from the Airport or the Atocha train station and Patricia was a really nice host.
But unfortunately the flat is really poorly insulated, in terms of noise and cold, and we could not sleep well, either because of parties in the building or rooms next door, either because of the high school in front of the window. Plus lot of light coming into the apartment in the morning (no shutter in the kitchen that is open on the bedroom) and the hallway smelling a lot of cigarettes.
I would recommend the apartment but for only one night or two in Madrid and if you plan to party and not to sleep too much ;)