I have stayed at this apartment for a long weekend city-break in Madrid.
The building is located within a residential area, thus with restaurants, supermarket and other services within a short walk. Also, it is very conveniently located right by Chamartin station (rail and underground connections).
The apartment looks as described in the website and is clean and tidy. All elements in the flat were working properly, with no noises from the neighbours or from the street (the apartment is located on an eight floor, and the lift was working properly). Ideal if you want to be close to central Madrid, but also a little away from the noise inherent to touristic places.
The host was very flexible both for my check in and check out, and was also replying quickly to any communication during the whole process, so I always felt attended. This was important in my case to solve a minor issue when collecting my keys at the concierge desk on arrival, as the employee on shift happened to be new and was not familiar with the collection procedure, so he was refusing initially to hand the keys and had to speak directly with the host to clarify the situation. Since the host was available on the phone and willing to help, as he did during the whole process, the misunderstanding was sorted quickly, but make sure you have at hand his contact details just in case.
I would have no hesitation in recommending this apartment for anyone visiting Madrid and looking for a quiet place to stay.