Sonia's place was absolutely wonderful. She was a terrific host - very kind and welcoming. The house is very clean and neat. The room is simple and faces a court yard and is quiet. I had an undisturbed sleep.
The location of the place is fantastic also - it is close to a grocery store (Sonia was nice enough to walk me there) and also there is a direct bus route to the airport steps away. The bus took about 30 minutes and was only 1.50 euros. The metro station by her house will take you anywhere in the city.
I would recommend this place and if I am ever back in Madrid (I hope to be) I will stay with Sonia.