I absolutely loved this opening, and how they set up the entire scene to make the change just pop out at you. Doing it in complete CGI and showing only the Pokemon was a big change in the feel contrasting to the anime's typical opening, but that's only half the story.
To me, it felt so very symbolic to have Pikachu the only thing in color, running across an entirely black and white world filled with shaded-out Pokemon. It deeply pressed the fact into me that this was an entirely new world, and that you (or Ash, in this case) is starting from zero, knowing absolutely nothing but ready to see everything. The Pokemon shadows in the opening also get colorized after the episode that reveals them, which really drives home that feel of the (spoiler-free) new generation, when you went on an all new pokemon adventure, just discovering things. I'm not too much of a fan of CGI, and the preview made me ask questions, but I think the quality is alright; the Pokemon look about as well as they did in Pokepark Wii or your typical Japanese commercial for the games or TCG (they usually use 3-D for those types of commercials). The fact that it's all CG made it feel less out of place than it usually does in the main parts of the Anime. Rica Matsumoto singing is nice, I preferred her solo XD. The song doesn't stick out to me that much, but the animation just wins for me.
Something tells me that, this opening being so different from anything else we've seen before, it's either going to be met with my reaction, or heavy disappointment, with very little middle ground. :P