I had a really great stay in Valentin's apartment! He was super accommodating and responsive by email and text (despite being in Japan at the time.)
The apartment itself is wonderful. The view can't be beat: Sacré Cœur on a hill in the distance and a cathedral just feet away. Although it is a studio apartment, the organization takes full advantage of the surface area so the kitchen, bedroom, and bathroom feel adequately separated and spacious. The clic-clac is easy to use and very comfortable; the kitchen is equipped and clean; the shower never ran out of hot water.
In all, this is a great place to stay for a young globe-trotter or couple in Paris! (Be aware of the six-flight walk up for those of a less sprightly situation.)