We stayed here for a month in May.
1st the location is perfect! We used the buses with a Navigo card which can be loaded with an app. Everywhere we wanted to visit was a simple bus ride from this central location, or an easy walk. We also made most meals at home and found plenty of excellent food choices all within short walks of the apt.
The kitchen has a cooktop, microwave, a small refrigerator but no oven. The space is snug but was not uncomfortable for us. The loft bedroom is also snug, has small stairs and might be difficult for tall people. The bed was quite comfortable. We of course read about the 5 flights of stairs and yes, they are formidable... but we got used to them eventually.
The only other heads up I would add is the living area windows of all the apartments look in on each other as they share an air shaft... we had a few noisy neighbors occasionally or smelled some smoke but hey... it PARIS! Its sometimes noisy or smelly but its beautiful and its alive!
I'll finish this review by saying Cecile is a good communicator and we would be happy to stay here again.