I just found out who the Champion is. That surprised me, somewhat.
Did you know that you can catch N's Pokemon? N's Pokemon have a different way of appearing, and when they are caught, the OT's name is 'N'.
I'm glad you don't have to go to the Dream World to get Hidden Abilities for Pokemon. Not that I ever pay attention to abilities...
And now each Pokemon has a "characteristic" that affects stat growth.
You can get a Zorua without an event. I'm not sure if that's good or not...
And now there is a Habitat list, similar to FR/LG's area lists.
You can customize your Trainer Card and set your "favorite medal".
There are six different Trainer Card versions. You get the second one by completing the National Dex. Getting the Black/White Card (depending on your version) is practically impossible for most casual players. For one thing, you actually have to win the Champions Tournament in the Pokemon World Tournament to upgrade your card.
You can draw a circle around a group of Pokemon in the Pokemon Boxes, and you can move all of the Pokemon in that circle at once. I don't think I've ever needed to move that many, though.
Pokemon Horoscopes? Really?
You can now add-on Rebels. So if you have 30 steps left and you use another Repel, it will automatically use the repel once the 30 steps are up. Useful, well, whenever you need to use more than one repel in a row, like Victory Road (if you aren't fighting Wild Pokemon).