Nathalie's place is lovely, as many other reviewers have noted.
Design is great, the apartment is spacious, comfortable and cool, and it feels like a home away from home.
The only negative for me was street noise from cars and busses, as the apartment is located on quite a busy road (albeit in a brilliant location). Having said that the noise doesn't seem to have bothered anyone else in the reviews, so perhaps I am just an overly light sleeper!
If you don't mind some traffic noise then this is an ideal place to stay in the Marais.