Where to start, where to start? First, it's a full-fledged sequel instead of twin deluxe versions, but even for those who thought it'd be the case, they're likely to be blown away. The game introduces a variety of completely new areas, as well as extra gym leaders. We know of two of them so far (their types are Poison and Water), and it's unknown whether they're replacements for old gyms or not. The scans also show a large chunk of Unova being buried under ice... gee, I wonder who's responsible for this? I have no idea!
The best news, though, has to be the Unova Dex expansion. A whopping 300 Pokémon are now featured in it (Platinum, eat your heart out), and you meet some of the old ones very early on. The new additions include the Tyranitar, Metagross, Weavile, Eevee, Lucario, Lapras, Golduck, Ampharos and Lopunny lines.
Of course, we have new protagonists, a new rival, and everything else that's expected out of a new game... overall, I have to say I'm impressed at the effort that went into it all, as it alleviates several complaints commonly leveled at Unova.
This also means that I'm almost certain to LP the first White at some point in the future - most likely after my Diablo break. Well... that's something I had definitely ruled out even two months ago, but the Let's Play that was never supposed to happen will happen.
Edit: By the way, I guess I should mention 80% of Unova being frozen. Here's my theory on the matter: This is pure speculation, but I'm under the impression that so much of
Unova freezing will only happen later in the game. You know, in the
mandatory "oh ****" segment where the crap hits the fan and it looks
like the villains are going to have their way? Because I can't imagine
so much ice being there from the start. Let's take a look at what's NOT
frozen: Castelia, Nimbasa, Driftveil, what appears to be the brand new
areas just south of Driftveil, Opelucid, and routes 4, 5, 6 and 16.
That's almost nothing!