We spent a week at Franck's flat and had a wonderful stay in Paris. The apartment is a gem - literally a tiny museum where you can sleep. Located only a quick walk from the Metro and in a neighborhood with interesting cafes and restaurants - you can grab a quick coffee before heading on sightseeing adventures and find some delicious dinner when you return.
The apartment is located on the sixth floor and it is steep and winding. If you've packed too many things in your suitcase, you'll regret having to carry it upstairs. There are exactly 110 steps from the front door to the upstairs, so pack accordingly. Also, if you're looking to catch up on sleep or need peace and quiet at night, you may reconsider this space. The bar scene outside is extremely loud and carries on all night long, until approximately 5 AM. I'm not sure if this is unusual, but during our stay, it occurred most nights except Monday and Tuesday.
The apartment was clean and well appointed. There is a washer/dryer in the unit which is a plus. The bed is not extremely comfortable (hard, lumpy pillows) and is quite small (American full). If you need more personal space while you sleep, you may be disappointed. Also, there is no air conditioning and it tends to get very warm during the day on the sixth floor. There are plenty of curtains and keeping the windows closed and curtains drawn does help keep things cool.
Overall, I felt very safe and comfortable and would recommend this rental with no reservations.