Stéphane apartment is probably one of the best places you can stay in Paris. There are no downsides, extremely well located, clean, beatiful, cozy and well equiped (wifi, hairdryer, iron...)!
Also, they were very kind an offerted us the opportunity to leave our luggage in their studio while we continue discovering paris our last day (our flight was late in the evening). The only possible thing that may be an issue is that the apartment is in a third floor and there is no elevator. For us this wasn't a problem at all.