The location is fabulous. The apartment is in the Puerta del Sol and walking distance (15 min) from the Prado and other museums. As others have noted, it is an interior apartment with no windows. This does make the apartment quiet as it is a vibrant and noisy neighborhood. However, the lighting in the apartment is not bright, which makes it seem dreary. This could be fixed with righter lights. The lofts are fine, but I would not recommend them for anyone with young children. The stairs are steep.
Juan Pablo was very communicative during the lead up to our stay and was helpful in extending our time in Madrid. However, we noticed that the sink in bathroom was very slow (essentially useless). I messaged (morning of day 2) him about it and he asked when we would be around (assuming he did not want us there during the repair). I responded that we would be out all day. No further communication and no sink repair. It is just okay, but not a great apartment.