Olivier's apartment is in a great location for those intend to spend some time in a neighbourhood where real Parisians live and work. The area of Ménilmontant is perfectly located near great parks, fast metro connections, and at the crossroads of neighbourhoods with different characteristics, for example Oberkampf with its bars, cafés and bohemian establishments, Belleville and its market and ethnic shops, and Gambetta, with its more family-oriented amenities.
We stayed in Olivier's apartment for five weeks, as I was in Paris for work, and it was a good choice for us as a family of three because it's relatively spacious (it has two bedrooms and a proper living room) and my employer was covering costs for accommodation for the entire time of our stay (Paris airbnbs are expensive, and this was no exception). The apartment was very clean and we were also able to have access to weekly cleaning (for additional pay) provided by Olivier's friend, who managed the flat in his absence and who was very nice and responsive.
Everything in the apartment worked pretty well, and our only minor issue was related to the presence of our daughter, who is a toddler, so we had to significantly 'baby-proof' the place while we were there as there are many objects and frames hanging from the walls. The apartment is on the fourth floor and has really nice big windows, but these are also fairly low in height, so we were a bit worried about keeping them open with our daughter there. Other than this very specific issue related to the presence of our child, we found the apartment to be comfortable, and the area surrounding it to be well suited to our needs and lifestyle (for example, my husband and I were able to go to the Parc de Buttes-Chaumont regularly for our running).
Olivier was really responsive when I had questions or requests. On two occasions, we had issues with noise from the apartment directly above us. Because the apartment is located in a very big tower building, Olivier didn't know these neighbours but he nonetheless offered to help remotely. I ended up going upstairs the second time this happened (the first time they went on until 6 a.m.) and it turns out it was a group of teenagers partying when the parents were away. When I told them to please stop at midnight the second time around, they did.
Overall, this was a good place to live while in Paris for work and with family, with some adjustments. I appreciated the apartment's cleanliness and the fact that everything seemed to work well, even though some things could use some updating (e.g. the hair dryer or some light fixtures, but nothing major).