The apartment is quite small but fits perfectly 2 persons who are coming to discover the beauty of Madrid for a couple of days.
PROS : Very central location, walkable distance to almost anything; Very clean; Easy and flexible check-in; Quite cheap; Comfortable; The host was very nice and offered us the possibility of leaving the luggage to their office until our departure.
CONS: The TV is very small (but I assume you don't need it anyway in a vacation); Early check-out (11 PM) with no possibility of delaying it); If you are traveling in the winter - the AC doesn't really provide a lot of heat in the room, although the temperature is good under the blankets - you are not going to suffer of cold, but you're not gonna feel the need to undress either. (We went in January)
For me the PROS where much more important and the price was fair. 5/5