We greatly enjoyed our stay at Fred and Nat's apartment! We met with them when we arrived in Paris and they went over everything about the apartment and surrounding areas. They even gave us a bottle of wine and some candied chestnuts to enjoy. They were quick to respond online. The apartment was a great fit for our party of 4.
The pictures and floorplan were completely accurate. Note that there is one toilet and two showers. The apartment is on the top floors of the building, with a small elevator one floor up from the ground floor, so be prepared for stairs or multiple elevator trips with luggage.
The location can't be beat, literally right next to Les Halles shopping center/metro station. Plenty of good food (including 1 Michelin star restaurant Benoit), shopping, grocery stores, bakeries and even some jazz clubs (Sunside-Sunset, Duc des Lombards) are in walking distance. Centre Pompidou is very close and actually you can see it from one of the rooms. Louvre is also like 10-15 minute walk away. We also just walked to Notre Dame in the morning. There are several churches around the apartment that hold free concerts on certain days. We went to Saint Merri to see a concert of dual piano performers.
If we come to Paris again with a group, I think we would stay here again!