First of all, the location is very good as it is located near the station of Montparnasse and the underground.
Secondly, the host could have been much more attentive because she didn't respond our messages until the previous day of our arrival. Moreover, she didn't received us, she just left the keys and gave us instructions to find them.
Thirdly, as far as the studio is concerned, the kitchen is very outdated and not clean at all. The kitchenware were old, dirty and we even found an insect between them !
In addition, the furnitures are broken (the sofas) and there are too many of them to such a small place. Therefore, we can hear all the neighbors as if they were in our studio. The studio is in the ground floor so we had to keep the windows closed so as to have some privacy.
Lastly, the main advantage of this studio is the price... Paris is expensive.