We loved our stay at Marine's apartment!
The location was incredible and exactly as described: near public transit, halfway up a side street near a busy corner, so it was both quiet and bustling. It's 15-20 minutes by metro or bus to any touristy attraction, and about 30-45 minutes walking. The restaurants in the surrounding area are incredible and well-priced, and there are also great takeout options nearby, too.
The apartment itself was excellently laid out and furnished. It's a spacious and well-cared for apartment, and though the bedroom has a curtain for a door the soundproofing is remarkable-- my boyfriend could be talking in the living room and the sound wouldn't travel to me lying in bed. The 1.5 baths are clutch, and the washer is a great perk, too. The place had everything we could have needed (a pleasant surprise: Marine was kind enough to provide many outlet adapters, and even a phone charger), and Marine's sister did a great job welcoming us and showing us the ropes. Communication with both Marine and her sister was easy and responses were quick.
Overall I can't recommend this place enough, and only hope that it happens to be available for my next trip to Paris :)