Overall the apartment is very nice and in a central location. My only concerns after staying there for two nights in June is the noise from the street and the heat. We stayed Friday-Sunday, and we found that there was a lot of noise from the bars in the street until 2am (when they close), and it also got quite warm (though in the summer Sebastien provides fans, which should help).
Otherwise, the apartment is very nice, with a truly impressive living room area with tons of natural light. It's in a very central location, which makes it easy to walk to things, or take one of the numerous metro and bus lines that are close to the apartment. Do be mindful of the fact that it's on the 5th floor (6th American) without an elevator. We didn't find that to be an issue, though it sure made for a workout!