Location, location, location! The view is superb (Notre-Dame, Eiffel Tower, Pantheon, etc). The apartment is nicely appointed and quite large for Paris. You can walk everywhere and there are several metro stops around. The RER B straight from CDG also stops around the corner at the St Michel - Notre-Dame station.
Antoine is very helpful and always willing to help. Check-in and check-out process are very easy and hassle free. Highly recommended!