I thought I'd just post this here for informational purposes. To go over what the different features of the new Unova Link are and how they work.

• Keys- These things are like semi-version exclusives. You unlock them as you progress through the game, but they're all there in the menu and locked as soon as you start up the game. If you can guess what they are, great job. They're all pretty straightforward, though. You can transfer keys through Infared between Black 2 and White 2 to get all the unlockables, but you don't get rid of your original when you transfer.
• Memory Link- This is a special connection between Black- Black 2/White- White 2. (You might be able to go mismatched with it, but I don't really want to try.) With this your form a connection with DS Download, like with Pokétransfer, except you don't have to do anything at all. The info from your original game is saved to your BW2 file, and it triggers events and cutscenes that reference things from Touya/Toukou's adventures through Unova and tell what happened in the 2 year gap between old and new Unova. There seems to be a list of events as soon as you make the link, but I didn't bother looking at them.
• Dream Radar- I can't really elaborate much on this, I can't afford Dream Radar XD But basically you just connect using your 3DS and it'll download the Pokémon you've caught with the AR app, just like the Pokéwalker. Still, can't speak out of experience.

I'll try to explain Dream Radar later, as I'll be getting it either tonight or tomorrow, most likely.

Already setup Memory Link.

Guess I'll be on the lookout for keys.

Pardon the poor quality, but I found an interesting movie reference. During the exchange between Skyla, whose gym is next to an airport, and Elesa as part of the Memory Link, there is an a reference from Airplane!. The original lines were, "Surely, you can't be serious" / "I am serious, and don't call me Shirley."

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Also, for Memory Link, you don't have to have two DSes. You could also make do with a computer and a wireless router if you use the Global Link way.