I only have good things to say about the host and this apartment:
The Host (Jose): Extremely friendly, helpful and thoughtful. He waited for me to fly into Madrid at 11pm so that he could personally hand me the house keys and show me the house. With all the choices of restaurants down the street, it was so much easier to follow his recommendations, and they were on point every time. As I had to leave one day earlier than booked, I asked if he could cancel my last night and refund me for it. He did it without any hesitation, and did not invent any excuse about the potential bookings he had missed because I cancelled my last night at the last moment.
The Apartment: It is an extremely comfortable loft, in one of the trendiest areas in town (while providing very effective sound insulation against the lively streets below). Wandering in the area, day and night, uncovered some of the coolest stores, and best restaurants and bars in town. Whether you are looking for a party, or an early night in, this is the place for you.
I definitely recommend this place, and if I were to go back to Madrid, I know where I will be staying!