Well, I did not expect to be able to write this so soon, but I was luckily somehow able to get my hands on Pokémon Y version recently. I've played through the first seven gyms and most of the main story, so I'd like to give you my thoughts.
This is arguably the best Pokémon game yet.
It's not perfect, it still has a little bit to go before that, but for the most part this is the Pokémon game fans have been waiting for since "Pokémon Stadium": a full 3-D RPG experience. If that makes sense to you, then you will adore this game.
The designers went all out on making Kalos feel like France which is both a good thing and a bad thing. Team Flare are one of the more ridiculous villains ever to grace a Pokémon game and I'm surprised their leader isn't obvious to the NPCs until late in the game. On the other hand, said leader is ultimately pretty scary in his nihilism so it evens out.
Mega-Evolutions are pretty neat, but since I usually comprise teams out of new generation Mons they have little use to me until I grab one of the other versions and do my Six Gen Run (Favorite three-evolution Pokémon from each generation in one team). Similarly to this is the awesome part early in the game where in addition to your Starter Pokémon, you can pick a level 10 Kanto Starter (Bulbasaur, Charmander, or Squirtle). For perhaps the first time in my life I chose my least favorite, Bulbasaur, because he complimented my team and I would have little problem boxing him when my full team was realized. Of course, in my Six Gen Run, it's Charmander all the way.
Super-Training is an awesome minigame. Pokémon Amie still baffles me but it's pretty cute. The route design is fantastic. I like a lot of the new Pokémon, though there aren't nearly enough of them. Fairy type manages to be intimidating and the new type match-up system inspired by them really does close a lot of loopholes in the old system.
In short, if you're a fan, you'll love this game. But you'd know that by now anyway.
P.S. They're teasing the long-awaited Gen 3 remakes so hard.