This location is unbeatable! You are within minutes to the Seine and minutes to some of the best restaurants and late night spots in Paris. I stayed for a month here and felt very safe! The 6 floor walk up is NO JOKE-- with a very narrow stairwell to get up so definitely keep that in mind.
Things that can be improved: Wifi, cleanliness
I work remote and this was an issue in this apartment. Since the bedroom sits one floor up, the wifi did not reach at all and in the living room where it did reach would only get speeds about 5/MBPS which is barely enough to hold a solid video call in its unstable conditions. It also went down completely a few times so be prepared to have unstable wifi.
While the apartment was cleaned before I arrived, it is just very old and has seen its share of use! There are also belongings from someone else throughout the apartment which was odd to me (very random items and papers, etc). It also smelled terrible when I arrived so had to do some work to air it out but eventually that went away.
Overall, I think the location/value of this apartment is worth it if you can deal with the wifi/cleanliness issue! You'll also leave in great shape with the walk up conditions :)