I agree that the visualiser is different now. I was watchin it last night and was truely AMAZING 😱 . With the crazy stuff it was doing it must work the system a lot more than the previous version.
They've changed the way size is handled. You can select any size (small, medium, or large) and it will fill the entire iTunes window, unlike before. iTunes lowers the resolution, but will blow it up to fill the window's extents.