The Louvre Apartment is indeed in a very convenient location in the 1st Arrondissement from which we were able to see Paris at our leisure on foot. During our 4 day stay, we visited the Louvre, Musee d'Orsay, Rodin Museum, Eiffel Tower, Luxembourg Gardens and Museum, beautiful cathedrals (Notre Dame, St. Sulpice, Ste Chapelle), Bon Marche; we also strolled along the banks of the Seine and through the streets of the Marais and around St Germain.
For those staying at the apartment, it should be noted that the entryway requires negotiation through two locked doors and a gate, some uneven spots (steps) and up a narrow circular stairway to the apartment. If managing heavy bags, this takes some muscle. The way in has timed lights which are required in the evenings, although the stairway remains dark as the light switch is located at the apartment level. This route also takes you past the back entrance to the restaurant kitchen (above which the apartment is located) where staff is sometimes working.
The apartment itself has two bedrooms with comfortable beds, comfortable sofa, dining table with chairs, and is equipped with most appliances, although no oven. The one bathroom is small, but includes the basics, including a washer and cleaning storage.
We did experience some repair and cleanliness issues, however, which we advised the owner about on our arrival (e.g., broken shower door/not closing fully, used dishtowels, knife not washed left on counter). He responded quickly, apologized, and offered to meet us and repair the shower. But our stay was already so fully booked that we said we'd manage as is, assuming repairs will be completed for next guests.