I stayed at Magda's place this December for 5 nights, and it was a perfect choice that I did not regret. San Telmo is definitely the neighbourhood you want to stay at when you visit Buenos Aires, and Magda's house was right at the heart of it, literally next to the Sunday San Telmo Feria and all the amazing bars and parrillas. Magda is the sweetest host - she will give you tips, and talk to you about the Argentine culture, and it definitely added to my BA trip. I also had the chance to practise my rusty Spanish. I loved Magda's dog Lola too :)
As some other guests have described, the room is right on top of the kitchen, reached by a metal ladder, and there is no door. I did not mind as my stay was so short, and I am a notoriously light sleeper. However, it's worth keeping that in mind. Having a separate shower for myself meant that I could pop in and refresh twice a day given the heatwave I experienced - very handy.
I would definitely choose Magda's place again in my next visit. Thank you Magda!