Overall, Mathieu's place worked great for us 3 adults. There was a problem learning how to lock the front door, but after Mathieu demonstrated how to do it, we had no problem. You have to lift the handle until it stops, then lean hard against the handle, forcing the door more tightly closed, while turning the key. If outside, turn the key clockwise. If inside, turn it counter clockwise.
Mathieu's place lives up to its description. Bed 3, the loft bed, is tricky for an adult, but my 6 foot tall, 63 year old brother was able to get up and down and to sleep there. Bathrooms and kitchen work fine. And the location is great - rue Daguerre has loads of shops, markets and restaurants, and easy access to the metro and the rest of Paris. I would stay there again.