I had a long stay here (3 weeks) and the apartment was very comfortable; the shower was easy to get to the right temeprature, the fridge was clean, cold, and large, the bed was comfortable and clean, there were PLENTY of additional linen, and the house was spacious. There is also a open swimming pool (cleaned regularly) that you can just walk up to and use freely. There is also a lovely rooftop area with a grill where you can watch the top of the city of Buenos Aires at night. The Air-Conditioning is top notch. The cooking area is ok, there is a hotplate that isn't great, but you do get a microwave, and a lovely automatic blender that you can use to make smoothies with the fruit you buy downstairs, right next to the house.
There were a couple of minor issues; the internet occasionally would stop working (likely not their fault), the TV was not hooked up to the antenna and thus had no local channels (or, i couldn't get it to work), and, the location is noisy. You do have an external balcony where you will spend most of your hot Argentinian evenings, and it's right on the street, and so it's very, very noisy. To be honest, there is a glass door you can close and shut out the noise at night, but if you want to use the balcony, it's gonna be loud. Unfortunately, it's just due to where the house is located.
Silvina was very helpful and would always reply to my requests very quickly, even at night.
Note that the apartment is within walking distance not only to amenities of all sorts (try the pastry shop downstairs), but also in a place where it's easy to reach the city center, and the metro is right around the corner.
All in all, i would say 4.5/5 - excellent for 1-2 visitors who want to do a lot of walking around and don't mind the occasional traffic noise.