We stayed for 8 nights, and it was really good, very clean, spacious, big tv for movie night when it was raining, good internet, big bathroom! Location was great too, we were able to visit all of madrid :)
The only negative was that the mattress was really hard, and I found that surprising for an airbnb I guess... I'd recommend adding a softer layer on top of it...
Another thing, pretty random but I have to mention it, not a complaint but an advice:
The windows and the closet doors go all the way down to the floor, like 0.5mm above the floor. I had never seen that...
Please be careful while opening them if you are not wearing shoes, I almost badly hurt my toes a bunch of times while opening them :/