The appartmens were great - it's located not far from city center and metro - you can easily visit most places without city transport. Inside the apartment is very clean and well-planned, very stylish.
The communications were smooth - Christian is very helpful and helped us a a lot. We didn't have problems at all.
The only point to mention is bar on the first floor just below the balcony - we visited Madrid at Friday-Sunday and till the very late night outside was quite loud. It could be a problem if you travel with children.