Good sides: the location is perfect to see the sights f Paris, it was clean, there were two baths, a coffee machine, and a table where you can have breakfast with tasty food from the bakery on the corner (after folding the bed of course).
Weaknesses: the apartment is for maximum 2 people (most comfortable for 1) to me, but definitely not for 4 people even two of them are kids (it is one standard room even divided into two); there was no place where to put our things - we kept everything in suitcases on the floor, which further reduced the space; the doors of the toilet, the cupboards and also the beds creaked, making the stay less pleasant; the sink in the bathroom is microscopic - you can't wash your teeth without everything around getting wet; there is a non-stop working ventilation, which is very loud (including during the night) and you cannot switch it off; the inner isolation is not ok and you can hear what the neighbors speak; very small windows and a bad view (but this is subjective I suppose). From the inside, the interior of the building itself is slightly miserable - very very narrow corridors and the floor was not flat (but also this is subjective, one could not see it as an issue). The communication was terrible, we received automatic messages but almost not answers of what we asked (I think it was mainly a robo chat, which only replay to keywords with automatic messages); we even got wrong codes and the check-in was kind of terrible adventure, and at the end we still have not received an excuse for this inconvenience....; there were two glass bottles on the roof-terrace (I guess left from previous guests), it was dangerous for the persons passing on the street because they could fall every moment, we wrote a message to the phone given for communication but no one removed them not even replayed (we could not remove them ourselves because it was scarry to go out on the roof from the window - i cannot imagine how someone put them there at all)