This was my first time using Airbnb, and it was a great overall experience.
Norma was a wonderful host -- extremely warm and helpful. She was very communicative leading up to my arrival, and helped me with any questions I had concerning my itinerary once I had arrived.
Location is extremely ideal if you either have an early morning departure or late arrival from Madrid Barajas. One ten minute bus ride brings you to within three minutes of her place. As the area is residential, it's quiet and very relaxed.
As for the space itself, the entire apartment is new, and the room/bathroom was simple and clean. No complaints there or anywhere else for that matter.