Overall a very good place. It is clean, bright, wide with high ceiling and the location is perfect (we mostly walked)
On the minus side, the sofa bed mattress is not really comfortable (quite thin, very bouncy, and you feel the springs in your back). It might be ok for one person only for a weekend but we were two persons in the sofa-bed and stayed 4 nights. Although prices for airbnb in Madrid are on the higher spectrum, we think the overall price was a bit high for a place which was not a real 4-sleeper.