A number of changes have been made to the UI since the Release Preview 2 weeks ago. Microsoft have said the new Metro UI will appear crisper following the removal of shadows and transparency. Gradients have been removed from buttons. The task bar is no longer has the glass, transparent look or blur effect. The new design brings with it some heartache for those that loved the Aero Glass effect as it has now been completely removed from Windows 8."
Link to Original Source