I stayed in the studio for a two-month lab visit and having the chance of living at this place greatly contributed to making me appreciate my stay in Paris so much.
The studio was exactly as described, very clean, nicely furnished (I like to talk about it as a miniature Versaille :)), and equipped with everything you need for your daily living. The location in the 9th arrondissement is amazing with a small but very lively street with lots of shops around the corner. Montmartre is just a few minutes away and at the same time, in terms of car noise, the street itself is very quiet which I feel is really a luxury in busy Paris. The metro line is very close, Vélib stations (rental bikes) are right next to the place and the Louvre is actually just a nice 30-minute walk down south.
Nathalie and Gilles were great hosts, very easygoing, and full of joy and helpfulness.
Overall, I don't think you can have much better in Paris than this studio!