Wonderful view, comfortable mattress, nice wooden beams, located right at the Metro stop... But, the apartment is significantly overpriced (not including the $30 extra per night for a third person).
The apartment is not quite in the Marais but in a neighboring quarter. There are some minor awkward space issues with the placement of the sink, etc. We happened to be there on nights when it was very hot. The fan in the apartment was broken, and the space is designed with little air flow. We were very uncomfortable and were up for hours in the night. (Julien provided a replacement fan for the next night but could have been more helpful and responsive.)
I would have been happy with this apartment had it been half the listing price. In all, we had a decent enough stay, but it wasn't exactly heaven.