We spent a really nice weekend in Madrid! The flat is very well located, spacious, clean and comfortable. I strongly recommend to stay in this flat if you want to visit Madrid easily (don't need to take the subway and a lot of super cool restaurants and bars nearby).
However, I have to mention two small problems: the flat is located on the ground floor (so it's a little bit noisy, especially during the night) and the wifi is really slow (sometimes it didn't work at all).