Flat is perfectly located, close to a few metro stations, shops, cafes and attractions. Álvaro is extremely helpful person, gave us good advice about places to eat and to visit.
The only things what could be imroved in the apartment is temperature (quite cold due to weather conditions and air conditioning and heater does not help really); bed width (no claims to the host, bed's really as described in the profile and may be small for 2 people); noise (quite noisy bacause of neighbours in the evening because the bedroom is close to their kitchen and the window from the bedroom goes into the entrance hall.
In general, flat is good if you're not afraid of noise and want to visit Madrid rather in the warm time of the year.