Overall, the apartment is in a great condition, amenities are as described and we found the place squeaky clean when we arrived. Everything was great, functioned well, and the building is very quiet, so you won't be disturbed while there.
The apartment is in the 13th floor of a high-rise, which turned out to be a good thing because it keeps you far from the hustle and bustle of the street, while still at a central location. The metro is very close, as is Plaza de Espana. We even walked to the Palace when we went to visit. There are restaurants and bars everywhere around.
We did have issues with getting into the apartment with the key-app, which only works on your phone and we had trouble activating it with roaming internet. Make sure you have the wifi information at hand when getting in. Also, finding it was a bit difficult, but I'm sure Daniel will fix the description soon. All-in-all, Daniel was a great communicator and helped us out on a few occasions we needed, and we ended up having a great time staying in Madrid. I would recommend this as a base for exploring the city.