I mainly notice the sluggishness in OpenGL-apps (compiz etc). Downgrading libx11 from 1.1.1 to 1.0.3 - like suggested above - did not improve the situation for me. The machine is question is a laptop with i915-based graphics.
-- Sluggish rendering since xorg 7.2 update https://launchpad.net/bugs/88815 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs