Our family of three had an absolutely perfect stay here. We were looking for an ideal home base for a ten-day trip, and this was absolutely that. The location is beyond perfect: the apartment is a quiet oasis with a gorgeous secret-garden courtyard full of birdsong, and you walk outside and are at Les Halles, with trains and restaurants and markets everywhere. We walked to Notre Dame, the Louvre, the Tuileries, L'Orangerie; we were at Versailles in an hour and Disneyland in 45 minutes.
Fang's communication and flexibility (and recommendations) were stellar, and everything you need was there and worked well. Just about every time we thought "I could use..." we found what we needed in an intuitive place, whether that was a fan or laundry detergent etc.
I will say that it's an unpretentious rather than a luxurious place—the furnishings are a bit shabby and all the rooms are small. But with a kid I was just as happy not worrying if she was going to forget a coaster etc, and the beds were comfortable and the showers great.
The only real caveat is that even in March we got a couple of mosquito bites and there's no way to cool the apartment without opening the unscreened balcony doors so if you are sensitive to them as my kid is, you should be wary of the summer months.