This was such a cool place! I only had one night in Madrid, and the flat is definitely central enough to enjoy some of the city's greatest hits. I was able to walk with my bag from the Atocha train station to the apartment, and then to the Prado Museum and Retiro from there. It's super close to the Reina Sofia and chique little shops and bars.
I arrived 15 minutes later than planned, but a woman was still ready to let me in right away. The flat is as cute as advertised, and it was plenty cool even when I was there on a warm day, contrary to what other reviews say. A fan was running when I came in, so maybe that hadn't been there for previous stays. I would caution people to be careful with the shower -- it can really shoot out at you if you mess with the dials!
Overall the place is cool and a great value. I'd stay there again!