I stayed at Serge's place with my boyfriend for 6 nights on a work trip, and the flat was great. It's clean and comfortable and fits 2 people just fine (considering we were only in mornings and evenings). The area is super practical and great to hang out, everything you need in at your doorstep.
Check-in was hassle-free and although a few things were missing in the flat when we got there, Serge made up for it and was extremely accommodating, and helped us out with our luggage after check-out. He also answered every message speedily.
I liked that the flat feels like a hotel-type of room with kitchen and essentials you might need, rather than someone's house, yet it's also very welcoming. You also have no steps to climb up to get to the flat which is a real plus in Paris...
I recommend!