Some things about this flat are spectacular. The rental management was superb, with InBeauParis and Jean-Nicholas providing detailed information well in advance, staying communicative during the stay, and effectively handling a couple of issues (one caused by us, one a problem with the water). We loved the location, convenient and in a non-touristy neighborhood with a park filled with Parisians and children in the back, lots of good bakeries and restaurants and shops, and reasonably convenient for transit and Velib (although bikes tend to get thin in this part of the city). The view is wonderful! The flat is very quiet and comfortably furnished, and we particularly appreciated having electric fans. Note that the stairs are tricky, narrow and spiral, and people with mobility issues might want to take that into account.
The reasons this isn't a five-star review are that the flat could use some repairs, the key access is awkward, and that there are clearly systemic problems with the building maintenance. We had no hot water for the last 2 1/2 days of our stay (and were more than adequately reimbursed for that), and saw a note in the lobby complaining that this is happening frequently. Another reviewer mentioned that the elevator was out during the summer. While not the fault of either the rental management or the owner, this is potentially pretty disruptive to a stay.