Awesome skin. I see what you were going for, but I would prefer you added a teeny little bit more contrast. I love the gray text color. but just a little bit darker gray - not black of course. Then you should work on the preferences and other menus. Add a border or something. The preference dialogue completely blends with the main environment. Now I see why Microsoft is reluctant to give us completely borderless windows. If you're going borderless, then there should be more contrast and shadows between layered windows.
Awesome theme. Thanks for the great work.