Mario and the other hosts were very friendly and professional.
I had the street-side room in the appartment. The street is actually a square with several bars and restaurants. At night there was some noise, but it wasn't too bad and it quietened down around 2:00.
The room and the appartment are well maintained and kept clean. The room has a door lock. For guests, there is a full kitchen available and a living room. Wifi was stable and fast enough for HD video streaming.
The bed was very comfortable. Not too soft, not too hard.
One thing I need to mention here is that an occupant of one of the other rooms has a dog. When you are afraid of dogs or you have a dog allergy, talk to Mario before you book. Also, you need to be able to walk some stairs because there is no elevator.
I was in Madrid for a stopover, so I only spent one night in this room. It was a good experience. I would also consider this for a longer stay.