Today when I uninstalled the Windows 8 Consumer Preview OS to install newly released Windows 8 Release Preview version OS and when I started using this OS I realized keyboard my responding very-very slow. I checked my keyboard connections and even replaced the keyboard by USB version but no use. After huge googling I found the solution that worked for me and the same I'm sharing this here.
(i) Open Control Panel
(ii) Click on "Ease of Access"
(iii) Click on "Set up Filter keys"
(iv) Click the Turn off Filter keys Check Box
And Problem Fixed.