x11-drivers/xf86-video-intel-2.13 is out and should be in the portage tree, especially since kwin 4.5 have problems(glitches and freezes) with the 2.12 driver version. see http://intellinuxgraphics.org/2010Q3.html Reproducible: Always Steps to Reproduce:
2.12.902 which is strictly identical to 2.13.0 was already in the overlay... Fixed in CVS.