I stayed here as a part of a group of five for a friends birthday. We were all very impressed. The space was minimalistic and spacious. The location itself is perfect - essentially everything is walkable. The one small issue we had was resolved in matter of minutes, and the overall service we received was extremely efficient and indeed fast where necessary.
The apartment was perfect for our stay and delivers and more on what is advertised. I highly recommend it.
(And I will add that Madrid is a truly amazing city).