All the more reason to get rid of the silly rounded corners. They're very 2000. If you look at the trends in design, you'll see that rich colors and clean edges are very much in vogue. I expect a lot more combinations of arcs and plumb lines as the interface continues to evolve, along with the replacement of dated-looking gel effects. Aqua is an interesting idea, but it doesn't really capture "water" in a contemporary interpretation. Instead, light and texture are the new directions.
For the people complaining about the "darkening" of the UI, just remember that this is a work in progress. No matter what they produce, some people are going to prefer the old style. As I've said before, I expect some particularly vibrant color accents in key areas with more subdued color elsewhere. You can't take advantage of color and lighting if everything is a happy, middling blend like it is now (bright greys and muted colors). The darker grey window colors set up much bolder system controls and room for lighting effects (which would lack contrast on a light base color). Richer colors create more dramatic environments (that means darker greys). We've already seen the beginnings of this (Front Row, Quick Look [the eye button in Finder], iPhone, AppleTV, Time Machine, the Apple Developer website, and others).
The brushed metal, the buttons on the bottom right, the uber cool button on the top right with it's cool animations...
