This apartment is beautiful, very classic Parisian with gorgeous views from the balcony and windows, and in a lovely and safe location very close to the Sacre Coeur and metro stations to get around Paris. There were four adults in our group, my husband and I took the sofabed while my parents took the bedroom. The sofabed was very comfortable, however I would say the apartment would be more ideal just for two people (also the shower is in the main bedroom).
The kitchen is tiny so I wouldn't recommend planning any elaborate cooking, but there are plenty of restaurants nearby. You also need to be mindful of the noise made by/on the old parquet flooring as it's very easy to disturb the neighbours.
We would definitely stay here again - in fact my parents are already thinking of rebooking!