With Microsoft’s new operating system comes a few changes, among others the Aero glass feature will be removed, to make way for a cleaner user experience. I think this is a good way to go for Microsoft, as I believe the glossy glass look has been used for quite some time now by Microsoft and their competitors for quite some while now, and it’s time for something new.
You can read more about this MSDN blog post: http://blogs.msdn.com/b/b8/archive/2012/05/18/creating-the-windows-8-user-experience.aspx . This blog post also explains how the user experience has evolved with the different Windows versions throughout time. Quite interesting reading.