Before we even get to the apartment, let's talk about Mike. Certainly the most accommodating host I've ever had on AirBnB, with an amazingly quick response to my booking request and later questions and changes to my reservation. Without even needing to ask, he provided us with a wealth of information on the apartment, the neighborhood, and the city in general. Really made the experience 10/10.
The apartment is fantastic in its own right: clean, right-sized, and brimming with authenticity. My favorite AirBnBs have always been those that really feel lived-in and not like hotels, and Mike's place fits the bill. Our group was 3 people (all singles), but the apartment can comfortably accomodate two couples without them tripping over each other. The bathroom and kitchen are tight but functional, so we managed just fine. And it wouldn't be a Madrid apartment without the balconets!
Overall - if you're on the fence, don't be. This place was simply great.