We had a fantastic time at Gregory's!! His place is an excellent position to all of the major sites (Notre Dame, Louvre, Eiffel, etc). Just north of his place are also some excellent dinning and walking options (of which he lists in his guidebook).
Gregory himself is very friendly, has a clean, well decorated, comfortable place.
My wife and I, two friends and their two and a half year old son all stayed there. This was our first stop, of our first trip, to France and it was fantastic.
Highly recommended.