So to echo most of the reviews of this apartment - it is located in a great, central area (close to a market and pharmacy) - and Josefina is a great host, great communicator and assisted us in every way before and during our extended 10 day stay in Buenos Aires.
The room was a perfect place to come back to each night after a day of exploration.
One thing I would advise and has nothing to do with the quality of this flat (and I think so would Josefina) is to not wear a lot of jewelry or carry anything expensive, flashy or important in sight during your visit around town.
I was wearing a simple chain around my neck which belonged to my grandfather (more sentimental than costly) and some hooligan ran up and ripped it off (could have been a lot worse).
This happened on our next to last day and up until then had felt perfectly safe every where we went. I guess this is a good tip for wherever you travel.
Otherwise we found BA charming and full of great people, museums and food! Took a great day trip by train to Tigre as well which I would also recommend.