The apartment was perfect for our short stay. The location must be unrivalled - as close to the centre of Madrid as you could hope to be (it is on Calle Mayor)!
Despite the location, there was no street noise at all due to the double-glazed windows (and shutters).
The apartment itself is nicely furnished and clean. Check in/out was very easy, and communication was great throughout.
It might feel a bit small if you were staying for a longer period of time (and there is no space for clothes storage etc) but for a short trip it could not be better.