First and foremost Fabian is a terrific host. He is responsive and has lots of good suggestions even for a few things we hadn't thought of like arranging for someone to pick us up at the airport.
Second the apartment is in a fantastic neighbourhood. It is walking distance to restaurants, grocery stores, parks, weekend markets, tango salons, a modern gym and public transit. It also felt safe, we didn't have concerns about walking home from a restaurant or from dancing late at night.
Third the apartment is pretty spacious which was nice as we were there for about 2 weeks. Having a kitchen was great for making a late breakfast before heading out to explore, and the air conditioning essential in BA's summer heat. Despite its proximity to restaurants and bars its also pretty quiet in the apartment. As another reviewer noted having an eye mask is a good idea if you want to sleep in as there is a lot of natural light in the apartment.
There are a lot of stairs to the apartment and to the loft bedroom. The stairs to the bedroom only have a railing on the wall side so are open to the living room. This could be an issue for anyone with mobility issues or who has has a few too many drinks in the evening. Happily there is a bathroom on the same level as the bedroom.
Basically we loved it and would happily stay at Fabian's place again.