Alvaro's place was perfect for us. It is very close to all of Madrid's tourist attractions: you can go pretty much anywhere on foot, or, if you prefer, the subway is really close. The house is really nice in a quiet and safe area (not that we encountered problems anywhere else in Madrid), and there are many places to eat nearby. There are also two well-stocked supermarkets open until 10pm nearby. Alvaro was a great host: he gave us some tips and advice on where to go and where to eat, and checked on un many times to see whether everything was ok!
However, there are two things you should keep into consideration, which for us where not an issue, but I realise that for some they might matter: the place is on the fourth floor with no elevator and the street is on a "hill", so you should take that into account if you have any movement impairment and the bed is more on the small side.
Thank you, again, Alvaro, for contributing to our great stay!