I ran this in October 2021, after two previous postponements with Covid. It was well worth the wait.
The route is just stunning. Think of almost any of Paris's many landmarks and the route goes past almost every one. From a start in a packed and pumped Champs Elysee, Le Louvre, Opera Garnier, Bastille, through Vincennes, back along the Seine and with the Eiffel Tower coming out from the sky at around 28k. You finish coming out of the Bois de Boulogne with the Arc de Triomphe in sight. They are testing this route for the Olympics in 2024 and that will be some spectacle.
I ran in glorious sunshine, and Paris like this is just sublime. If you get that, you will have the race of a lifetime. The course was well stocked with water and food stops, and cake in particular every 5k or so was a big winner.
The expo is out in Porte de Versailles, but was well organised and big enough. Only gripes are needing to get a doctor's certificate for it, issues with the website/app service. The medal is sadly a disaster: essentially just advertising the sponsor, trying to be kooky (I think(, has little to identify with Paris and is made as cheap and as flimsy as possible. A medal for a city like Paris shouldn't be hard to do well, but this one is the worst I have seen. I'd probably run it again just to get a proper one.
Nothing but good things to say about the city itself, other than try to stay a day or two after to properly enjoy it. And when booking hotels, there really isn't much difference in size and quality for a lot of them. Booking the location is key; ideally away from the main tourist spots where real Paris still exists. Many of the hotels will be exactly the same anyways, unless you can afford something very special.