I had a wonderful time at Sophie's place. The flat is incredibly warm and charming and the host kind and welcoming. The room is quiet (no noise from the street as the window opens on an interior court) and the mattress very comfortable. I slept very well each night.
The flat is very conveniently located 2 min from la Bastille's station, which means that you have immediate access to most tube lines but you can also walk on Rue de Rivoli, towards la Tour Saint Jacques, l'Hotel de Ville or the Louvre. Two boulangeries down the main door of the building, one facing the other, are also worth noting and just around the corner the area is full of good value bars for aperitif or dinner.