I stayed in this apartment for 7 weeks during the summer, and it was a great experience! The apartment is perfect and everything you could possibly need is available. From the window you see a beautiful Parisian street and you really feel like you are at home. The neighborhood is calm but close to metro stations, supermarkets, cafés and restaurants. Within a few minutes (or a bit longer if you don't like stairs...) you can walk to the Sacré Coeur and the center of Montmartre, but the apartment itself is outside the touristy area.
The hall and staircase of the building looked a bit old and messy, I had the impression that there was a renovation going. However, the apartment was tidy and well-organized. It's large enough for two.
Michael is a great host, he is very friendly, helpful and easy to reach.
I'd definitely recommend this apartment and I love to stay there again some time!