We stayed at Pierre's place for four nights and were perfectly happy. The location in the 11 arr. is really great, just off Boulevard Voltaire, easy to find, just a few steps from a metro station in a fairly quiet street. There is some little background noise at night but - sleeping with open window - it did not bother us in the least.
Close by is Rue de la Roquette, a thoroughfare to Bastille, with myriads of opportunities to have dinner.
The flat was clean and well-equipped. 4th floor means climbing up a typically narrow flight of stairs, which should be taken into account when planning to arrive with huge luggage.
Communication with Pierre was straight and easy and he made sure that everything was okay.
We can wholeheartedly recommend Pierre's place.