I was renting the place for my family. We planned to stay a few days in Paris. The place is very central and very nice! It has everything you need, and it gives you the feeling of typical parisian place. The stairs are steep, but you get used to it :) There is just one apartment per floor in the building.
Apartment is located on the third floor, or the second parisian floor. I would say it wasn't noisy, but I guess during spring-summer it might be somewhat noisy, as there are several restaurants around. On the other hand you have lots of restaurants, fresh bakery, small grocery shop, and lots of shopping. :)
Location is amazing! It takes you literary 10-15 minutes to walk to Louvre, around 20 minutes to Opera and so on.
And a few words about hosts. Dominique and Catherine are very nice and sweet people. They responded quickly and tried to make our stay in Paris very comfortable.
I would recommend the place and hosts to everyone who wants to spend time in Paris!