I get display glitches with xf86-video-intel-2.20.13 on my Gentoo Linux system. They vanish when downgrading to xf86-video-intel-2.20.12. I'm going to attach a couple of screenshots after submitting this bug. They show an empty Mozilla Firefox window, but it's not a Firefox specific thing. You should look closely at the address bar borders and at the close button "X" cross. They look ugly with 2.20.13, but they look good with 2.20.12, instead.
I don't know if it is related, but my system also have bug 57054 with 2.20.13.
Some additional informations:
# lspci | grep VGA
00:02.0 VGA compatible controller: Intel Corporation Mobile GM965/GL960 Integrated Graphics Controller (primary) (rev 0c)
$ uname -r
xorg-server package version: 1.13.0-r1.
Please tell me if more details are needed.
Created attachment 70543 [details]
Display glitches with xf86-video-intel-2.20.13
Created attachment 70544 [details]
No display glitches with xf86-video-intel version 2.20.12
*** This bug has been marked as a duplicate of bug 57054 ***