Excellent apartment in a great location. Situated in a upper middle-class residential neighborhood, felt very safe and walkable. Central location for visiting numerous parts of the city. Close to bus lines (though we didn't use the buses), restaurants and full size supermarket (on Santa Fe between Riobamba & Ayacucho). Plenty of taxis available on Juncal and Callao.
The apartment is located in an up-market building with elevator access. The living room / dining area is a decent size with adequate seating. The two bedrooms are not overly large but certainly more than satisfactory. The two bathrooms are functional with relatively modern fixtures. The kitchen is not huge but two people can work simultaneously in it. There were individual air-conditioning units in each room and these worked well. The WiFi was adequate (speed tests indicated about 8 Mps download). It went down one morning but Carlos organized for timely assistance to fix the problem when the normal reboot everything didn't work.
The only slightly funky things were: (1) the second bathroom is through the kitchen and a bit of a walk from the bedrooms; and, (2) the supplies of basic items (toilet paper, washing machine detergent) were extremely limited or non-existent (this seems to be a trend among AirBnB hosts these days). Additionally I think there is at most one English language TV channel.
Check-in and check-out were both easy; prompt, efficient and timely.
Overall an excellent apartment - stylish, comfortable and more than adequate size - in a nice building in a nice neighborhood. Definitely recommend it.