As for the location, the neighborhood is fantastic and beautiful, but the building is just above a street tunnel that was not so pleasant.
As for the experience overall, on our last day we had a problem with a leak (toilet flushes) coming from the back of the toilet, really annoying. It was our last full day in Madrid and we weren't planning to stay at the apartment and wait for the tenants to repair it, so I reported this problem right after we left. Due to this experience and cleanliness in general, I will not recommend this option to stay.