I travel a lot using apartments and I can say that this apartment is very well equipped.
Beds are confortable.
Size is very good for a family with two young children (40-45 sqm is a good size for the Paris standards).
Extremely clean (floor, equipment, sheets).
Owner allowed us to stay after the check-out since there was none after us (this is not always granted. So thank you).
I strongly recommend this apartment.
Pay attention on Montmartre position if you have young kids and you have a stroller: you need to take many metro to travel all around Paris and very few metro stations have lift or escalators.