We spent ten days at Mathilde's and Aymeric's apartment in late March. Great location! Besides being at a walking distance to the Louvre, Notre Dame, Saint Sulpice, Saint Germain des Pres and the Luxembourg Gardens, the RER train takes you straight from the airport (CDG).
Mathilde was very responsive and patient, she took the time to answer the thousand of questions we asked before booking.
The area is nice and safe. Plenty of bistros and cafes and book stores, there is also a supermarket (Monoprix) a couple of blocks from the apartment. Bon Marché is also near.
If you want to visit further away places, the metro station is very near.
The apartment is well equipped, pretty much as the pictures show. It's a 4th floor without elevator, nice exercise if you go in and out a lot, as we did.
We did enjoy our visit to Paris and would recommend this apartment to anyone.