By far one of the top apartments I've stayed in in Paris. I did not meet Thierry but communication with him throughout my stay was flawless--besides, his neighbor was around and available to help.
The location is top notch: multiple metro and bus lines are within a 5mn walk, and grocery and specialty stores are right on the street, including a dry cleaner, tailor, etc. The Belleville neighborhood is one of the liveliest with lots of bars and restaurants of various kinds. The Buttes Chaumont parc is great for a run or to hang out, as is the Canal.
The apartment itself offers a calm and relaxing environment. It is very spacious, including a large kitchen and bathroom, and well isolated with almost no street noise. The balcony was definitely the highlight, particularly when the nice weather came back. With its numerous plants and large table it was a quiet oasis to have a meal, coffee or drink while enjoying a beautiful view of the city.