The flat is itself practically perfect for staying in Madrid; it is excellently located and a close walk from the station, central area, museum area, park - essentially anywhere you would want to go!
It is also somehow superbly cool and quiet, despite being in the centre of Madrid during what was a hot and busy week in Madrid, we had absolutely no issues with noise or temperature (we didn't even use the aircon during our stay!).
The place is spotless and well maintained, with all the amenities you could require (including an excellent dishwasher).
Overall, 10/10!