The flat has all amenities needed for a short or longer stay. It is on the fourth floor so be prepared to walk up some stairs, but it's no hassle and being so high up means you get no street noise. This time of year (November) it can get cool at night, but it was warm in the flat with the heating on.
Javier was a great host, he was kind enough to arrange for an early check in when he found out we would be arriving to Madrid early. The apartment is very centrally located, near loads of lovely bars and restaurants, and a walkable distance to all the major landmarks.