Denis' place is lovely. It is well equipped, nicely decorated, and very quiet, even with it being smack in the middle of the bustling Marais--the best place to stay in Paris, no question! The apartment is a very short walk to the St. Paul Metro station and to three supermarkets, a wonderful patisserie, and several greengrocers if you like to do your own cooking. If not, there are dozens of great restaurants within a five-minutes walk.
Denis is very flexible, attentive, and communicated back in a few minutes--a great host overall. We love staying in his place and will surely try to do so again on our next trip to Paris.