UI elements should be unobtrusive. Easily seen, but not garrish... and uniformity is key. I don't mind the colors, but the size of those icons is ridiculous.
I want Apple to decide on a standard for their UI already. They're getting there, but you can still see remnants of previous OS versions floating about... the toolbar in Disk Utility is a good example of this. Colored icons, versus the gray, minimalist icons of, say, Mail or Safari. The iWork apps also have these colored icons, and they look horrible, out-dated.
I hate to say the M word, but Microsoft's 2007+ Office apps demonstrate a better presentation of colored UI icon elements while also maintaining high-quality and uniformity. You may not like them, but at least they don't look like icons from the days of Windows NT.