Fanny's apartment is in the perfect location--walking distance to almost all the main tourist attractions. For that reason alone, this is worth it. She and Antoine are also very responsive and gave really good instructions for using the metro/RER to get to their apartment from the airport.
I would be really careful about looking at the photos before reserving, though. The bed situation is not quite as depicted. To get on the bed, you need to climb a bookcase that isn't bolted to the wall or the bed, and it does shake a bit as you climb. The bottom step has a lamp on it, which makes it a bit of an awkward climb down (especially if you're short).
This is not an ideal place for a tall person--there's not enough clearance under or around the bed if you're over 5 ft 4, and the corners of the bed are really sharp. Because you can't turn on lights from the bed, and it's unstable getting down, these corners are risky--my partner (6 ft 6) was getting out of bed early morning, thought he had cleared the bed, and ended up whacking his head pretty badly on the corner of the bed. (Getting up to use the bathroom in the middle of the night? Maybe not your cup of tea...)