If upgrading to xserver-xorg-video-intel broke X or made it very slow, make sure you are not using a PAE/bigmem kernel. The Intel driver now enforces UXA for acceleration. But UXA requires GEM support in the kernel, and GEM is not compatible with PAE before 2.6.31. So if you have PAE in your kernel (CONFIG_HIGHMEM64), i.e. for instance if you are using a -bigmem kernel, your Xorg.0.log will say: