I'll be sooo happy when this one particular spandrel is removed (photo credit @chrisvazquez7).
My office window faces it. It's not dirty, it looks that way after washing; I have no idea what is actually wrong with it, but it's been like that for years.
I'm with you @Edward Skira -- it has joined the blue-to-black anonymous glass curtain wall crowd. The new trimmings look well enough on their own, but that powerful air of distinction is gone. I do like the evergreen trees and the monumental blocks of limestone depicted in the rendering.