If you are looking to stay at an apartment that is right in the center of Montmartre with a great view (especially in summer, when you can enjoy time on the balcony) this apartment is great.
The apartment is mostly windows with a little bit of walls between them - so if you love that: it's perfect. We didn't think it was especially noisy but we were there in winter.
But it is probably not the place you specifically want to chose if you are aiming to relax in a quiet surrounding - simply because it really is in the middle of everything. But then again - why chose Montmartre in the first place. ;)