Me and my daughter (6 years old) stayed two nights in Xaviers room. It was even more nice than it appears in the pictures. It was easy to find and the instructions for checking in was easy, the equipment in the apartment was very nice and ideal for me and my daughter.
The room was nice and there was very little noise so it was easy to sleep. Also the location of the apartment was superb - only a few minutes walk from Bastille metro.
When I return to Paris I will definitely check to see if I can stay at Xaviers apartment once again.