Location: Quiet residential street in the 6th arrondissement. Close to several metro stops, including Saint Placide, Rennes, Sevres-Babylone. We had a baby and stroller and used the buses extensively which were convenient as well. It takes about 20 minutes to walk to the Musee d'Orsay and a little longer to Notre Dame. Also convenient to Jardin du Luxembourg, this is great if you have kids.
Apartment: The apartment itself is small, but functional. The bedroom feels a little worn, tired and the mattress is on the floor, which could be a problem for some, but was fine for us. Kitchen has dishes, pots and pans etc.
Check-in: Our check-in was a little frustrating as I was communicating with Christine through AirBnB, but a third party (who had not been to the apartment before) met us for check-in. In the end, we only checked-in about 30 minutes late (we were waiting inside the vestibule and they were in their car), but frustrating after a tiring day of flying.
Bottom Line: This is a good budget option in Paris and has good access to public transportation. The apartment is small and a little tired, but overall it is a good value. Don't expect a lot of host bells and whistles that you sometimes get else where.