The Les Halles location is perfect. Spacious apartment on a fairly quiet street (quiet enough at night for a good sleep). Plenty of shops (butcher, cheese, patisserie, boulangerie, grocer, chocolate!!), restaurants and metro all around the corner. Good walk to Seine and Louvre, healthier walk to Eiffel Tower and Arc de Triomphe. Apartment is clean, with stairs and tiny elevator and building is secure.
There is no air conditioning but it was definitely not needed as we opened the windows for a nice cross-breeze. We were there early July but wasn't super hot while we were there. (55-78F/12-25C)
One bed, no exaggeration, is 4 feet up. Our teen loved it.
Eric was very responsive to our questions (how does the washer/dryer work?! and clarification on the WiFi code).
I would stay here again and highly recommend Eric as a host!