We had a very pleasant stay in Julio and Sarah's apartment in Madrid. They made sure we could pick up the keys to the apartment at a café nearby, which made the check-in very convenient and flexible. The apartment was small and a little dark, but clean and cosy. If you just need a place to sleep, it's perfectly fine, and the location is great.
(Oh, and if you like cocktails (or beer, or rum) and a good old tropical-island-vibe from the 50's, you should visit the Kona Lei tiki-bar at the opposite side of the street. It's kind of a weird place, with a kitchy but also strangely beautiful Hawaii-theme. It was totally deserted, when we were there, but we loved it. And the bartender was really nice.)