Although we only stayed with David for one night, we found him to be a very welcoming and helpful host. He was there to greet us at his front door as we arrived, and then helped us with our luggage to our room. Our room and bathroom were very clean and comfortable, and the location of his apartment was excellent - very easy to walk to many main sites, like the Palacio Real (Royal Palace) and Almudena Cathedral.
We ran into David as we were returning from a nice walk and he told us of a choral performance he was going to participate in that evening. We decided to go as well and it was wonderful - an a cappella performance of sacred music performed by 33 people in a nearby church.
We would highly recommend staying with David if you are in Madrid.