This is a fantastic place to stay!
I stayed at Frederic's for 2 nights and he was so welcoming while I was there. Before my visit, he replied promptly to any queries. I just completed a French language immersion before arriving in Paris, and he was kind and generous enough to let me try to speak as much French as I was able, even though it wasn't necessary.
His place is in a cool neighborhood, really close to a Metro stop, as well as 2 major train stations. I felt comfortable walking back alone into the later evening.
The apartment is spotless, beautifully decorated, and the bathroom has modern fixtures.
He makes you feel right at home to use all the common rooms, and he is friendly and happy to chat. I loved that he was glad that I didn't just stay in my room when I was there. That said, I loved my room too. Good size, nice view and comfy bed.