Kouign Amanns aren't a Dominique Ansel creation obviously, though their version does compare OK with good ones in Paris.
I've had cronuts several times and have found a wide variation in quality, which isn't particularly surprising considering how delicate they are. At their best, they are a world class pastry, very flaky with a perfect filling (really like the blueberry lemon). Another time it was overly heavy with the filling making it a bit soggy (I think it was Dulce de Leche). Certainly worth getting if you're a pastry lover - but if you are someone who "loves" the croissants at your local bakery, it's probably not worth the wait.
I've also had the misfortune of trying a few imitations from places like Paris Baguette - garbage.