My partner and I spent 4 nights at Ana and José Antonio's place, on our first ever visit to Madrid. We had a fantastic stay.
The flat is excellent: lovely space, full of light, every possible amenity, comfy bed, sparkling clean.
Ana and José Antonio were excellent hosts to match: although we didn't have a chance to meet them, they were super friendly and easy to contact. Among other things they were kind enough to allow us some flexibility over check-in times (particularly helpful as we were arriving at different times of day and had lengthy journeys behind us); and José Antonio was incredibly patient when we couldn't figure out how to work the induction cooker (only because the latter is way more sophisticated than either of us...).
Finally, the flat is located in a friendly, colourful neighbourhood, which we had great fun exploring. Worth noting: it's very close to the metro and to the main train station (so airport transfers are easy), as well as a 24-hour Carrefour. The Parque del Retiro is within walking distance (we went running in the park every day). And within even shorter walking distance are a number of very friendly tapas bars, cafes, and a lovely quirky indoor market (Mercado de San Fernando).
In sum: highly recommended!