Just returned from a whistle-stop visit to Madrid. We absolutely loved the location of the apartment. There is a little noise from the street below but we found it ambient, at night, rather than intrusive. The mornings noise was a bit more irritating but we just shut the windows and it seemed to do the trick. The apartment itself was lovely. Very well appointed and clean. There were 4 of us and it was comfortable. We had thought from the pictures that there was a bedroom with 2 singles and a separate common room with a day bed but we were wrong. There are just 2 pictures of the same room, set up differently (single bed format and 2 singles).
The apartment was really close to nice shopping street, and on the other side, Plaza Major. only 1 minute to either. plus only about a 3 min walk to Mercado San Miguel which was brilliant for breakfast pastries (must go on a diet tomorrow) as well as other tapas. Very busy but a must-see spot.
Would definitely stay here again if we return soon and would recommend (with the caveat that there are many steps up to it as it's on the third floor) to other travellers looking for a lively bolthole.