The apartment is really nice, well equipped and had everything you need for your stay, specially the kitchen (which we didn't use much since we were in Paris... ;)
The elevator is really small, but worked well to help bring our luggage upstairs.
Sébastian was a very attentive host, responsive, easy to communicate with and allowed us to keep our luggage until later the day of our departure which was really helpful.
Belleville is not a very central area but it has a lot of live of its own, and the apartment is 5 min walk to the metro, which brought us quickly to the center.