I really like the Windows 8 enahncements to the Windows Explorer interface. The ribbon feels natural to me and the idea of having it minimized initially gives you a lot of extra screen real estate. It allows me to show the Details Pane on the right as a standard setting as most screens are 16×9 or 16×10, so wide.
But I have one minor tweak to suggest, since I often want to quickly switch between the Details and the Preview pane, why not add a small button to both switching to the other? Here is a small mockup:
I know I can add the commands to the QAT, but having them in place feels much more intuitive.