I stayed for about 2 weeks in the lovely area of Palermo - Las Cañitas sharing the apartment with the even more adorable Inés.
Cañitas - It's a safe neighbourhood and so far, I didn't feel uncomfortable when coming home after sunset. There are several supermarkets within 5 min. walking distance and you can choose between Subte D or several buses to discover the city. Parks are nearby so you can do outdoors sports whenever you feel like. Small cafés and trendy restaurants are very near and you even have a shopping mall just 2 blocks from the flat.
The apartment/room - The flat is spacious and you can enjoy the huge kitchen and its amenities as well as the living room. The room is small and clean (cleaning service once a week) and comes with a twin bed, desk and a closet that is able to fit clothes measuring about two huge suitcases. It does not have a TV but you can use the lovely books or the hifi-system in the common areas (with latin music) to entertain yourself. One thing to be noted is that the room is directly fronting the main road which makes it rather noisy, so you might want to pop in some earplugs if you suffer from light sleep. You have a small (sufficient) bathroom with shower and toilette for your own use which is definitely a plus. There is a laundry around the corner if you may want to wash your clothes.
The host - Inés is lovely company. She is a talkative (really good English) and open-minded lady that loves to share experiences and as she is a sociologist you will always find yourself in a long an interesting conversation. When I first came to her place, she equipped me with whatever I needed (train and bus map, SIM card/phone to make local calls, etc.). Inés has been hosting students for years and therefore is used to sharing her home and assist in the most cooperative way.

All in all, I enjoyed being here and will actually be staying longer than planned. I can warmly recommend staying with Inés if you enjoy a nice chat and a relaxed atmosphere in one of the safest areas of Buenos Aires.