The new Pokemon are alright, I guess. I liked the Gen V pool better. There weren't nearly enough, either. (I'd rather have more meh ones just to have more.)
I wasn't that impressed with the 3D rendering overall. Other than in Lumiose City, it might as well have been in Gen IV/V-style pseudo-3D, since only in Lumiose can you actually be in the same place and have the camera angle change (by approaching it from different angles). That was neat. Lumiose is also HUGE, which I encourage them to continue.
I wish there'd been more to do with the roller skates. You learned a couple tricks and then... that was it. It didn't show up much later.
The pacing was strange. There was a TON of space between the first and second Gyms (and also a lot before the first), but after that the game moved very quickly.
Team Flare was horrible. They didn't have a convincing goal or any interesting characters, their theme was repetitive and annoying, and they showed up at seemingly random times, often unnoticed by other NPCs. (In Geosenge Town early on, for example.)
Count me in for the lack of post-game material. The Looker missions are kind of a nice diversion, but I wish they were harder. It just ruins it for him to tell you exactly what to do. Getting a competitive team is fun, though, and occupies a lot of time.
A summary of my opinion of the game is that it contains a number of neat ideas that weren't taken far enough. It's still Pokemon, though, and as a result I still love it.