The apartment is very nice and in a great location - very central and easy to walk to most of the sites you want to visit in Madrid. The neighbourhood, Malasana, is very cool with many bars, cafes and restaurants on your doorstep.
The only small gripe we had was with the internet connection - this was almost non-existent at times and when we did get onto the wifi it was very slow and kept cutting out. This however wasn't too much of an issue as free wifi is available in many places in Madrid.