We stayed eight nights in Arnaud's flat and were very happy with the accommodations. The apartment is infinitely cool with the stone walls and unique basement with plenty of amenities. We had four guests during our stay and had plenty of space, which can be hard to come by in central Paris. There is plenty of restaurants, shops, grocery stores, and watering holes in the neighbourhood all within steps of the apartment. It is close enough to many sites to be able to walk (The Louvre is about a 20 minute walk away).
The neighbourhood is diverse and lively but felt very safe even late at night. The closest metro station is a two minute walk away (and the Paris Metro is incredible for getting around quickly). The flat is on a quiet side-street so very little vehicle or walk-by traffic left us with no noise issues.
Arnaud has a list of great places nearby and his communication before, during, and after our trip was very good. One minor issue we contacted him about late one evening was dealt with within minutes.
The kitchen, while small, is well-appointed and has everything you need to cook and serve any meals you decide to make. There is a full-sized fridge for groceries, toaster, coffee maker, induction cooktop, microwave/oven combo, and a bunch of dishes, cutlery, and glassware. The Livingroom has a table with four chairs, a pullout sofa, coffee table, and a television with some kind of internet television box (we never really used this). The main floor bedroom has two twin beds that can be pushed together and a shower (which is a unique layout, but the shower is very high quality). Rounding out the main floor is a water closet that's a bit of a tight fit, but saves a trip downstairs. Blackout curtains and a set of shears offer privacy and darkness as needed.
The basement has a WC, large bathroom with laundry facilities, and a large bedroom with two bedrooms and a lounge chair that also converts to a bed.
All the beds were comfortable and the linens were of good quality. The apartment was spotless upon arrival and renovations must be fairly recent (within a couple of years). Everything was in good working order and you can tell that there are efforts made to maintain a high level of quality.
This space is a real gem in Paris especially if travelling with family or a group. Skip renting a car, stay central, and use public transport/walk. It's a great way to experience Paris and Arnaud's place is an excellent home base.