We very much enjoyed our time at the apartment. The location is perfect - right near everything you’d want to see in Le Marais and only a short 10-min walk from the Seine (we took the Batobus every day, which I highly recommend for getting to/from the main sightseeing spots). The apartment was clean and just as advertised. Louise was incredibly responsive, which we really appreciated.
The only things that might be helpful for future visitors to note is that the building’s residential rubbish bins are located right next to the front door, so staring quite early in the morning, other building residents may be dropping off their rubbish, which can be noisy. Also, the lovely, small courtyard that the apartment opens onto seems to be the place for people to smoke, so occasionally smoke wafts into the apartment (unavoidable, since the door must be at least partly open to maintain air flow). These were minor considerations, though, and we would definitely return.