I have booked the apartment for my brother and it was perfect! The apartment is totally lovely and cosy. It is located right in the center of the Montmartre, but the street is very calm so you will not here anything from outside.
Alain was very nice and pleasant. He took care for my brothers stay and he was very helpful to give him tips for going out and to have lovely days in Paris.
I just can recommend the apartment. It was the perfect place to stay!