My stay of 3 months at Agustin's flat was perfect. I had rented for a long period following an exchange in Madrid.
The location is great, the tube is near at 250 meters and the train station too, easily to get to the city center Sol, Callao etc or the airport. beneath the building, you have also access to all commodities (groceries, coffee, bars, bakery etc)
the flat is very calm and cleaned by a cleaner every 2 weeks.
Super warm and friendly host. in addition, he is super flexible.
The best place to rent if you come to study in Madrid or just to spend your week-end. I highly recommend.