It's hard to beat the location for Le Cocon. This is a locals neighborhood, so you're really immersed in real Parisian life. The Parc des Buttes Chaumont, which is just down the street, is breathtaking and I spent many hours there during my stay. It is so peaceful! The street is very quiet, but just a few steps away there are groceries, several great cafes, restaurants, etc. If you continue on down the Rue Belleville, you've got a really diverse neighborhood with lots of offerings for restaurants (French, Tunisien, Chinese, etc.) If you need to get into the center of town, the metro station is around the corner and it's about 10 minutes to Republique and 15 minutes or so to Chatelet.
There's a lot of space in the apartment and the kitchen has everything you need. There are several grocery stores close by (including Lidl which is less expensive than Monoprix). I should note, the bed is about 3-3 and 1/2 feet above the ground and there's a kind of uneven stool that you use to climb up. I got used to it after a while, but it might not be optimal for persons with limited mobility.
Overall, it's a really lovely place and I sincerely hope to have the chance to stay here again!