We loved the location and "look and feel" of this place on the south side of the St. Germain neighborhood. Everything was clean and well maintained, and Berit, the property manager, was very responsive and helpful (for example, when we mistook a 9 for a "g" on the wi-fi password).
For those looking for a great place to leave from and come home to when visiting Paris, this is a great find. Walking distance to some excellent cafes (5-10 minutes), and the main center of the city (Notre Dame within 15-20 minutes). Or the metro is close as well. The apartment is across the street from the Senate and Luxembourg Gardens. The street is a little busy in the mornings, but the room is high up enough and the windows seal to keep out the sound if you want to sleep in. Be ready to lug your suitcase up a tall spiral staircase. The five windows with multiple views were a big plus--we hadn't seen this feature on many other alternatives at this price range.
The fold-out bed was comfortable--no bars in your back. They had two fitted sheets and no top sheet, so we had to use a fitted sheet in between us and the comforter. Maybe something to check on before you arrive. The bathroom was small but updated, with the classic French "no doors" approach to the shower. They had a full kitchen (which we didn't make use of).
All-in-all, a great experience and a comfortable place from which to see the city. We would seriously consider returning if we visited again.