A great place! Romain and Solene are great hosts and they make sure that you have a great experience at their place. The flat is very cozy and you're just a few minutes away from Sacre Coeur. The street and the surrounding area also have a good selection of bakeries, restaurants, and bars. The unit is where the hosts actually live, so it offers a very genuine and local Airbnb experience in Paris.
The only heads-up I'd give is that the unit is on the top floor and there is no elevator, so you will need to carry your luggage upstairs. Having said that, I had a heavy luggage and even with that I'd totally recommend this place!