My wife and I had a wonderful 6-day stay in this lovely apartment with our 2 teenage daughters. Our host was very accommodating, spending time upon arrival to show us the apartment and orient us to the neighborhood.
The location was fantastic in the heart of St. Germain -- easy access (within 2 blocks) to RER and Metro stations. If you like to walk (as we do), location is super convenient as you are within 3.5km of: Arc de Triomphe, Eiffel Tower, Louvre, Tuileries Gardens, Notre Dame (closed for renovation), Le Jardin du Luxembourg, Musee d'Orsay, Musee de l'Orangerie and much more. The only transportation we took while in Paris was the RER to Versailles and the RER stop is 2 blocks away and takes you directly to Versailles. There are plenty of places to eat in the neighborhood. The bonus was an amazing Boulangerie on the ground floor next to our building for fresh bread, croissants, and other amazing pastries as well as espresso, cupaccino, cafe au lait and more.
The apartment is a duplex over the host apartment. As described, the apartment is on the 6th floor with no elevator access except for the host bringing your luggage up on arrival and down on departure. It was very clean. We are a pretty fit family so it did not bother us. Both bedrooms on the 1st level are well appointed and have a small balcony with amazing views out over St. Germain to the Eiffel Tower. The kitchen area, also on 1st level, is tiny (not great if you plan to cook a lot) with a microwave, small electric stove top, small refrigerator, small dishwasher, and a mirco washing machine (no dryer, as noted on listing). The 2nd level, on top floor of the building with big skylight windows for great natural light, is an open room, with table & chairs for eating, tv, sofa bed.
Overall, if you don't mind stairs, we had a wonderful stay and would recommend the apartment.