The apartment was in the perfect location if your plan is to walk Madrid. Practically all of the major sights were in walking distance, and the metro station was really quick to get to as well, for getting around to places farther away. There's also several grocery stores, an enormous number of restaurants, and large shopping areas within walking distance as well.
The apartment itself had everything we needed (and nothing we didn't), and Carmen was a really thoughtful host. We were a party of five (three kids six years old and under and two adults), and it was the perfect space for us.
We loved every minute of our stay and would highly recommend this place to other travelers!