In case you missed this as I did, Intel have released an updated beta HD Graphics Driver for use with Windows 8.
I installed this on my Samsung Series 7 slate and many of the graphics related glitches I saw have gone away.
These drivers may come in handy soon as the release of the Windows 8 Release Preview is happening soon. Its possible that the Release Preview build has even newer drivers in the build than these, but it is unlikely.
32-bit download – http://downloadcenter.intel.com/Detail_Desc.aspx?agr=Y&DwnldID=21235&lang=eng
64-bit download – http://downloadcenter.intel.com/Detail_Desc.aspx?agr=Y&DwnldID=21180&lang=eng