I had a great time at Joseph and Clara's place. The room is large and lovely.
The apartment is really nice and very typically Parisian, which is cool. It's also in a great location - really close to the Seine, Notre Dame, the metro, restaurants, cafes and supermarkets. (Top coffee tip: Strada Cafe, which is only a few streets away.)
Joseph was a lovely host (I was staying in Clara, his sister's, room) and as a born and bred Parisian, he has a wealth of knowledge about the city.
I'd definitely recommend staying here - particularly if you want an authentic Parisian experience.