Jean-Marie's studio apartment is small, but in an awesome way. It's extremely efficiently arranged, well thought out, and stocked with everything you need. The bed is a fold-out couch, but it is the most comfortable fold-out couch I've ever slept on. The ceilings are high, so you don't feel very cramped in the space. The flat is near silent, a real rarity for Paris. The only noise you hear is during the day people discarding bottles in the recycling, and the only reason you hear that noise is because it is so quiet otherwise.
The location is great, there's nothing amazing in the immediate proximity of the flat itself (e.g. the boulangerie next door is not the best in the area), but it is 5-10 minutes walk from many great things (Montmarte, Gare du Nord, multiple metro stops, good restaurants).
Jean-Marie was extremely easy to communicate with and was always available to answer any questions. I would stay here again without hesitation.