I had a really great time in Madrid, and the appartment of Mike was really great!
From the appartment it is a 10 minute walk to the main attractions in Madrid.

The appartment is not quite big, but clean and very comfortable when you are on a citytrip. The beds are perfect, which is (imho) "key" when sleeping abroad.

Mike provided us with a lot of information upfront and reacted very quick on questions (in advance and during our stay). Self service checkin was very quick and the information about Madrid was more than sufficient.
If you consider booking a hotel: don't! You are centrally located and you can have breakfast in the citycentre!