To clarify a few things, the twins originally had a Clefairy and a Jigglypuff, not a Chansey. XD (And GymLeaderSilver, the twin encounter theme is remixed from GSC, not RBY/FRLG).
As for the video, the intro was nice and all, but I kinda hoped they'd revamp the old GS intro. Still, the overhead shots of the cities was neat, and the bit with the Dogs and Eusine/Unown was great, and it was like a little nod to Crystal in the way Unown and Suicune were a bit emphasized in its intro. Hopefully, the two are more intertwined now.
Route 37's theme sounds great, though I think it's that same old version from one of the PokeSunday videos with that little cheery note in the middle somewhere. It's still good, though. The Twin/Lass/Picnicker encounter theme I recognized right away, and it sounded just like the GSC version. I loved the Trainer Battle theme, though. As for the levels and Pokemon they have, I have to ask: why does the Psychic have a normal-type Dunsparce? Hopefully, that's just for the demo, and they'll also be a bit stronger/at the levels they were before in the real game.
Well, just another month or two until the Japanese release...I need to figure out where to buy a flash cart. XD;