Great location! Right next to Mercado de San Miguel. Big enough for 2 (and a kid) and has everything that you need over a long weekend.
Some negatives: It is not really up to the host, I know, but although it is at a nice square, in front of the house there are some big selective trash cans/containers, which is not a nice view (eg neither 2 toilettes filled with bottles next to it in the morning when you look out), also it comes with noise when bottles are thrown in, or it is emptied in the middle of the night, - if you are a light sleeper.
When we were there it was pretty cold (3-7C) which is really not typical in Madrid, but the place is not optimized for heating, and the a/c did not seem to be cleaned for a while either...Also there's some mold in the bathroom as the shower is leaking and you can somewhat also smell it.
Overall still good value for money, flexible check-in, reasonable check-out time, communicative host, awesome location!