I can't stand the monochrome icons in the solution explorer either, its too hard to pick out what each icon is. I can see how someone who could extract no semantic meaning from looking at that explorer (i.e. a designer) might think its great, but for a coder? Its a disaster.
Even from a design perspective the icons are ugly. The folder icon for instance is horsey - perhaps because of the huge expanse of black. The file icon for C# is redundant as it is on a file with .cs extension and its not showing its a file.
I think what this is all showing, is that metro doesn't work for complex UIs and blindly enforcing it is causing a lot of pain. Theoretically I like the idea of a lack of chrome and clutter, but the practical implementation is definitely wanting.