Our stay at Paula's was great : the communication was very easy, Paula always answered very kindly and quickly. She was also flexible with our check in AND check out hours, which is a big plus.
The flat itself was really cosy, and felt like home. Le location is amazing, everything is at a walking distance, with a supermarket right in front of it.
The only thing was, the nightclub next to the building was noisy, so you should definitely buy earplugs if you want to stay during the week end but I guess it's more quite during week days.
Despite this little inconvenience I would recommend Paula's flat, and would stay there again for my next trip to Buenos Aires.