Stephanie and Hervé's flat is absolutely phenomenal. A short walk to Notre Dame, easy access to multiple metro stations, shopping is right around the corner and there are dozens of restaurants nearby. It was clean, cozy, quiet and the best part of our Paris trip.
The *only* downside to the apartment is that is accessible only by stairs (no lift/elevator) which means if you have any physical limitations the apartment may not be ideal. The walk up the 6 flights was worth it, though, for the rooftop views and Hervé was gracious enough to help with our baggage.
For the price or even double the price they asked, we could not have stayed in more wonderful accommodations.