Our plan to see all of the great sites in Paris in 5 days meant that we didn't need to spend our money on a lavish, expensive hotel. We needed a place to shower, clean our clothes, prepare breakfast and sleep. Jonathan's apartment accomplished all of our requirements. His flat is in a great, safe neighborhood, less than 1/4 mile directly north of the Notre Dame Cathedral. The space was comfortable for 2 adults and our 11-year-old daughter. Having a washer/dryer combo machine in the apartment meant that we each could pack VERY lightly; one backpack and one small bag for each of the three of us. The apartment is a 1-minute walk to the Yellow Line subway, "Estacion de St. Paul." West of the apartment is Le Forum des Halles, a huge mall (worth a visit!) that is connected to Châtelet–Les Halles, one of the largest underground train terminals in the world. The walk from the mall to the apartment is just under a mile, and can be made on three different parallel streets, each with dozens of restaurants, cafes and bars. The nightlife in this neighborhood is great, with lots of young professional-types, street performers and no signs of anyone that appeared to be "unsavory." We felt safe.
The bathroom has a shower with soap, shampoo, towels and toilet paper provided by Jonathan. The galley kitchen has a refrigerator, 2-burner stove, sink, silverware, glasses, plates and bowls. The bedroom featured what would approximate a full-sized American bed, and a closet to hang your clothes. The couch is "L"-shaped, but has a feature where part of it pulls out from under it to make a rectangle that was perfect for our daughter to sleep on. It might work for an adult, measuring about 4x6 feet when in the bed configuration. There is a grocery store right up the street to the west, several cafes, bakeries, fruit stands, sandwich shops, and a gorgeous cathedral a few doors west. I bought milk, cereal, juice and fruit for our breakfast, and we consumed all of our other meals out in the city.
This apartment is a good value if your travel philosophy is to rent a "crash pad" and spend as much time out in the city as possible. It was less than half of most of the hotels that we found in the area and considerably bigger, with a kitchen and washer/dryer, which for us, was key.
The only caution that I have is that the apartment is on the 7th floor, and there is no elevator. My wife and I are in our early 50's, and in less than average shape, and managed the climb without trouble. As I mentioned, we packed very lightly and climbed the stairs once a day, upon our return from the city. If you have to carry several huge, heavy luggage bags up the stairs, this may be a consideration.
In summary, Jonathan's Airbnb is a great value, in a great neighborhood and close to most of Paris' best sites. We will book his flat again next year if it is available.