We stayed in the flat for 9 days with three people and loved it. Andres is super communicative and helpful in recommending places around the city. The flat is perfectly situated and surrounded by lots of fantastic restaurants/bars, cafés & shops in the heart of Madrid. Inside, the flat is super quiet and exactly as described with everything you might need. Sleeping there with three people also worked perfectly. Since the price is also fair, I would absolutely recommend staying there.
The only small cons for us were that the wifi wasn't too fast (can be tricky if you are planning to work) and that the flat is not super bright inside, since it is situated in the inner courtyard. But since we were spending most time outside or at cafés anyways, we also didn't really mind too much.