The apartment was in an excellent location, within walking distance from really nice places (and the metro entrance right across the street was a huge plus for me). It's really safe (I walked the area around 3 am), and even though there's a construction site next to it, the noise only starts when you're supposed to get out and walk the city and ends before you get back.
The place is small, but it's fine for a one-person stay. The bed is comfortable and the heating very useful.
The only issue I had was with the wifi, which I couldn't connect to (Fosca was quick to reply and tried to assist me, but in the end we couldn't make it work). And also (and this is a bit more personal), the water pressure in the shower was very low, so showering was not as pleasant as it's supposed to.
Fosca was very easy to reach and helpful from day one, with instructions to get the key and nice details, such as a box of Pims and printed recommendations and directions for differerent useful and interesting places.
In all, it was a very possitive experience and a great value for money. Would definitely recommend to anyone travelling alone in a business trip or wanting to stay in a great location in Paris in a private place.