I am giving this place 5 stars all the way, but as others have said, it is important to be aware of those stairs up to the 5th floor.
The hosts are great, very accomodating, and quick to respond. We were met with the keys by a sweet greeter named Eva, who spoke English well.
The apartment is in a truly great location. A real neighborhood with a very Parisian (as opposed to touristy) feel, with wonderful cafes, bistros, restaurants, small supermarkets, and shopping abound, along with very easy access to public transportation. It is also in walking distance (20-30 minutes) to many attractions such as Montmartre, les Passages Couverts (covered shopping passages) on Boulevard Montmartre, les Galeries Lafayette Haussmann with their wonderful rooftop terrace, shopping along Rue de Rivoli, le musée du Louvre, Place de la Concorde, the River Seine, the Quartier Latin etc.
The decor of the apartment is quite charming and ecclectic, lots of art and books on the walls and shelves, along with plenty of plants for a cozy vibe. Since the building is old, the apartment is worn down in places as can be expected, but it certainly was super clean. The kitchen is tiny (too tiny to cook anything but maybe pasta and sauce in my opnion), but well equipped with coffee maker, electric kettle, two burner glass top stove, fridge, microwave, and all the dishes and utensils you could need. TV and Wifi also worked well throughout the entire place.
It is a dual-level space, with kitchen, living room, and toilet downstairs. Upstairs you will find a loft style bedroom and tub/shower with a slanted ceiling. The shower space is very small - I am 5' 10" (1,78m) tall and had a hard time standing up and an even harder time to get in and out of it, due to a fixed plexiglass pane that only leaves a small triangle shaped opening to wriggle through.
A nice surprise was the air conditioning unit in the bedroom, especially since we stayed during a warm spell in June. The bed is on the small side for two people, and given that it sits under a slanted ceiling it feels even smaller, but there are skylights in said ceiling which let in light and air. There is also a downstairs couch to sleep on should you be feeling too cramped.
As stated above, my husband and I thoroughly enjoyed our stay here, and I think people who go for a personal and "lived in" vibe, as opposed to a stylized boutique hotel feel, will love it here. Yet due to the 95 steps to the 5th floor you will end up climbing several times a day, with luggage and maybe groceries at that, I recommend that you should be reasonably fit, with a good back and knees, before booking this place :) .