Fabulous location. This apartment is in a quiet part of the "center of everything." Very close to the major museums, the Retiro Park, and many many bars and restaurants. If only for the location I'd recommend this apartment in a heartbeat. The apartment itself was simple but clean and nicely decorated with IKEA type furniture. At night the front bedroom got street noise from the bar downstairs but that's fairly common in these older parts of town.
My only complaints (small ones were the lack of toilet paper (one roll in the whole apartment for a four night stay) and one bath towel per person (we were 2 ppl). However once we asked, they delivered more right away. Unlike some airbnbs this one didn't have "extra" amenities like a surplus of leftover toiletries or condiments. However, one cannot expect such extras.
I would stay here again regardless of the towel and toilet paper situation. Again the location is truly fabulous.