Recently, I have observed some misconceptions and incorrect information circulating. I will try to correct this with the information I have available.

-Sylveon is pure Flying type. Its ability is Prankster, and it has quite a few status-effect moves. I have seen production art of it flying by using its ribbons as a propeller.
-Bonding is a new feature within the game, but it is only the old Friendship system now with a slight effect on stats. An Eevee will indeed evolve into Sylveon via this method.
-Fusion evolutions are a major new feature; approximately one quarter of the new Pokedex is comprised of them. These work through use of a key item acquired later in the game.
-SpotPass and StreetPass are integrated. They are primarily used to download new trainers to battle and to operate an expanded Join Avenue-type feature.
-Limited character customization is possible. The height, weight and hair color of the character can be set at the beginning of the game, similar to how a Mii is made, and clothing can be changed at the player's house at any point. More clothing can be purchased at the game's Department Store.
-Rotom receives three new formes: Computer (Psychic/Electric), Bug Zapper (Bug/Electric), and Lantern (Steel/Electric).
-The dragon that was once Kyurem, Reshiram and Zekrom together is not in the game, but the original form of Genesect is. It is a separate Pokemon, a pure Bug type grasshopper-like creature that looks little like Genesect. This Pokemon is set to appear in the next movie and will be formally revealed in May.
-No secret bases, but room customization has returned.
-Game Corner returns, but the games no longer involve any sort of risk. There is a skee-ball game and a whack-a-mole game (using Drilbur and Excadrill, I really liked this touch) and Voltorb Flip is unlocked in the post-game.
-Cycling Road spans much of the region and can be used to easily travel long distances. Several points in the story require this to be used instead of Fly.