My brother & I stayed at Oscar's place a couple of weeks ago during our first trip to Madrid and we loved it. Communicating with Oscar was very easy, he answered all of our questions in a timely manner. The list of house instructions was very detailed and easy to understand. He even gave us numbers to two cab services which was extremely helpful when it came time to go to and from the airport.
The place is very clean and organized and looks the exact way it does in pictures and it's also in a very good location. There's a 24hr supermarket as well as a few cafes and bar/ restaurants which are walking distance from the apartment.
Getting to and from places was very easy from where the apartment is located. There are two train stations close by and it's a 15-20 minute walk to most museums and shops. I would definitely recommend Oscar's place to anyone looking for a nice and convenient place to stay while in Madrid!