What the new-look Aero gives back
Much has been made about the scaling back of Aero, both for aesthetics and power consumption on portable devices. The Aero subsystem, which was introduced with Windows Vista, hasn't been completely removed; the underlying window-compositing functionality remains. But some of the fancier effects, like rounded corners and blurred glass effects, are dialed down or absent completely. The Release Preview of Windows 8 offered an Enable Transparency option in the Personalization control panel's Window Color and Appearance pane, but it has been removed in the final RTM code. Turning off transparency reduces battery consumption, offers visual consistency between the classic desktop and Metro, and translates to fewer UI elements to keep track of and render properly, making your system that much more responsive.