Me and my boyfriend just came back from a great stay in Leo's studio.
It is clean, in a great position in St. Germain (one of my favourite Paris neighbourhood) but still in a quite street. Leo was very reliable even though we didn't meet her in person, and quickly replaced a hair dryer that had broken down.
The only thing I could say is that the studio is really small, and the toilet is in a room that opens up directly on the bedroom, which is not a problem if you are confident with the person you are travelling with and if you are more interested in going around than staying at home!