Antonio's place was the perfect place for our stay in Madrid. It was centrally located, and we could easily walk to the major sites, yet the area itself wasn't touristy. We were a stone's throw from a square filled with bars and cafes that turned into a local market on Sunday morning, and loved shopping and eating with the locals.
The apartment itself was also so cute, with the blackboard in the kitchen where everyone could write their names.
The only downside was that we only got one set of keys, so when one of us (who shall remain nameless) decided to stay out doing karaoke and wandering the streets until 5am, he had to wake the other one up to get back into the apartment. :p