I stayed 3 nights in Madrid. The flat is pretty central and close to bars, restaurants, etc. Also, it is very well connected to the underground and close to the airport. We received it clean and even with two beers in the fridge. I totally recommend it.
The ONLY SMALL CON: It is located on floor -1 which means you do not have sunlight coming and it is humid. If you stay for a few days it should not be a problem.