Location, location, location. This place was indeed in the heart of La Roma, walking distance to great restaurants, cafés, and bakeries (including Panadería Rosetta, highly recommended) and also a few blocks from a subway metro station. Everything you need to have a good time is walking distance.
The apartment was large and very nicely designed. The bed was comfortable. The views of Plaza Rio de Janeiro from the windows give you a sense of fresh greenery in the middle of the city.
The host was very responsive and flexible with us, even as we were changing dates at the last minute.
Overall 5 stars.