First things first: Julien is a perfect communicator and will answer everything you ask him. We had a bit of tricky situation because he wasn't around to give us the key in person so he sent the key via mail from France to Germany - that was just amazing and worked out great!
The flat itself is very conveniently located directly at metro 7 (Place Monge). From there you can get in 15 minutes to the Louvre. There is a supermarket three houses down the road, a great Chinese takeaway place and some nice cafes.
As the flat is up top on the 6th floor you get a great view of southern Paris. And there is an elevator so you can save your energy for exploring the city instead of climbing stairs. The kitchen is small but very well equipped with all appliances you need to cook a meal, prep breakfast, make coffee or even wash your cloths.
Living and bedroom - each decently sized for a Parisian flat - are fully furnished (dining table, small couch, coffee table, king size bed) but more practical than cozy. But there are lovely details like the book hedgehog (loved it!).
Only downside is the bathroom which is very small and can get quit cold if it is cold and windy outside. And it is not as modern in appearance as the rest of the flat.
We would definitely recommend staying at Juliens, if you are looking for a good starting point to explore the city from as it is located perfectly for that. You can even walk home form Notre Dame in about 20-25 Minutes - parfait!
If you are looking for a romantic and really, really cozy place in the city of love this might not be the right Airbnb for you.