The biggest pro of the apartment is the location!
5 minutes walk to Pompidou Center, 5 minutes to Seine embankment, and 15 minutes to Notre Dame.
The apartment is small but very comfortable, you can sit on the balcony to drink tea and eat a croissant bought in the morning in the nearest bakery (there are many). A lot of flowers, we really liked the interior design.
Self-check-in and check-out at any time.
Keep in mind that this is the 6th floor through a spiral (beautiful!) staircase, a cold floor in the apartment (take slippers!), and a cramped shower room.
In general, we liked it very much! Location is killing all minor cons.