The update has two fixes. The first one fixes a compiz CPU usage regression. The second one enables unredirection also for Intel and Nouveau users using the Mesa 9.0.x stack. That means up-to-date installs from 12.04.2 LTS installation media and anyone with original 12.04 LTS installation who has opted in to the 'quantal' package updates of the kernel, X.Org and mesa *)
The new default setting for the unredirection blacklist is shown in the image below (CompizConfig Settings Manager -> General -> OpenGL). It now only blacklists the original Mesa 8.0.x series for nouveau and intel, plus the '9.0' (not a point release).
I did new runs of OpenArena at openbenchmarking.org from a 12.04.2 LTS live USB. For comparison I first had a run with the non-updated Mesa 9.0 from February. I then allowed Ubuntu to upgrade the Mesa to the current 9.0.3, and ran the test with both the previous version of Compiz and the new one released.
12.04.2 LTS Mesa 9.0 | Mesa 9.0.3 | Mesa 9.0.3
old Compiz | old Compiz | new Compiz
OpenArena fps 29.63 | 31.90 | 35.03
Reading into the results, Mesa 9.0.3 seems to have improved the slowdown in the redirected case. That would include normal desktop usage as well. Meanwhile the unredirected performance remains about 10% higher.
*) Packages linux-generic-lts-quantal xserver-xorg-lts-quantal libgl1-mesa-dri-lts-quantal libegl1-mesa-drivers-lts-quantal. 'raring' stack with Mesa 9.1 and kernel 3.8 will be available around the time of 12.04.3 LTS installation media late August.