Microsoft announced recently that they're dropping the resource-guzzling Aero Glass from the Windows 8 UI. Aero Glass is a feature first introduced in Windows Vista, and was brought over to Windows 7. It features gradients, reflections, and transparencies, and it really improved the look of the interface compared to Windows XP and 2000 (in my opinion, at least). The main reason for the change is to match it more with the whole Metro theme. Microsoft is "flattening surfaces, removing reflections, and scaling back distracting gradients." According to the blog post, we'll see the change in the soon-to-be-released (rumors say within the next month) Release Preview, but we won't see everything they're changing. Some stuff they're going to surprise us with.
Microsoft said that they went through hundreds of different ideas on how to change the look, and this is the one they settled on. They wanted to reduce the amount of clutter on the screen so concentration can be kept on the upfront application, instead of having a billion windows all over your desktop vying for your gaze. Above is a picture of how Windows 8 will look.
Personally I'm glad Microsoft is trying something new. Not that I don't like Aero Glass, but I prefer changes in UIs. While the new UI isn't the prettiest, at least it's a change. Hopefully the new interface will be less resource-intensive, which will speed up the OS quite a bit. If you want to read the full blog post, go ahead and check it out here.