We stayed at Kristian's Sunny Apt. a few days ago for two nights. The apartment is located at the center of the Old Town, a few steps away from all the major attractions, but secluded from the main crowds. As they say, Madrid never sleeps and this is true, so we could hear noises at night, but this come with staying in the center of a big city, so no complains there. The apartment itself was not big, but comfortable for 4 people (we were traveling with two kids), and have all amenities necessary to make your stay comfortable and easy. The pictures are accurate depictions of the space, so we did not have any surprises.
Kristian is an excellent communicator. Right away, he help us to figure out our way from the airport, and answered almost immediately all of our questions. Once, in the apartment, he made sure we were comfortable, and make himself accessible if we needed him.