I have to agree with Potato and Geo's suggestions.
I like the idea of a set of colors per project, with a difference between layouts/event sheets so in a blink you make the difference.
I also understand what tokinsom was saying at first and what animmaniac noted too: there's some lack of contrast between the enabled and disabled black ribbons/menu icons.
I used, in a blink, to know if a project needed to be saved or not before.
Now, it's less readable in an instant, it needs "identification".
But as animmaniac notified it, I'm confident he will fix the issue in the next releases, thanks in advance for that.
I use semi transparent window borders thanks to aero, and the black icons don't contrast that much over the blurry background, maybe tokinsom is "suffering" from that too.
I also get the impression that "black is a bit sad" or I don't know how to word it exactly.
As tokin mentioned, the UI used to be "shiny colors", the passage to black gradient makes it more "sanitized".
Don't get me wrong, it's not a big deal to me (apart from the save icon issue I mentionned earlier) but it's the feeling I'm getting from the new UI. I'm not telling it's bad work, it's different.
I still need to get used to the new objects/behaviors icons too (to spot them as Intrepid said in his post, I was quite used to the former representations).
Also a lot of plugin makers will have to redo their icons, to match the new color/symbol code.
As of now, built-in and custom are visualy struggling in the dialogs ^^