I lived for some days in Arlette's flat in Rue de Poitou in Le Marais. It is almost perfect situated in this very lively and charming part of Paris. It's in walking distance from Place de la Bastille and the Pompidou Museum and whatever is in between.
The flat itself is very small but cozy and worth the 82 (!) steps it takes to get there. It's very quiet as it's placed in the back yard of the building.
Arlette is easy to catch and communication is easy as well. She had some wifi problems though as she was on holidays abroad, but her caretaker was just as responsive and a very nice person.