I had a very good time in Nadine's apartment (being there for work). The location is perfect, close to public transport, grocery stores and restaurants. As a woman travelling alone I felt safe in the neighborhood, even at night. The apartment is in walking distance to the Palais des Congrès (ca. 15 minutes); and 2 Metro stations and a bus stop are a few minutes away.
The apartment is very small but cosy, functional and quiet (apart from the background noise of a big city). The toilet (just outside the room) is shared with other people on the floor, but this was not a problem as it was kept clean.
I recommend Nadine's apartment and will certainly consider staying with her again should I come to Paris again.