Comment 5 for bug 242990

Unfortunately the xorg.conf you've included contains a lot of overrides for things xserver now autodetects, and it's possible some of your overrides could be causing these problems. I would encourage you to first reproduce this bug with a stock xorg.conf (i.e. move aside your existing xorg.conf and then generate a new one using `dexconf` (you might need to re-add some of your InputDevice settings, but keep the number of alterations minimal)).

In particular, doublecheck your vertical and horizontal sync rate settings, as those especially can cause problems like these.

You also mention that some are running compiz. It's hard to say without seeing screenshots, but there's already well known tearing issues with compiz with 3D apps (bug #96991) I can easily reproduce that on intel 945 hardware.

While it probably seems like this is an xserver bug since you're seeing it with multiple combinations of hardware and drivers, in my experience these issues tend to be highly driver-specific, and similarities in symptoms are often coincidental. Even if it does turn out to be a xserver bug, it's more likely to get addressed upstream if we treat each case separately as driver issues. So please file separate bug reports for each case, against the appropriate driver, attaching all relevant information (minimalized xorg.conf, Xorg.0.log, screenshots, etc.) See http://wiki.ubuntu.com/X/Reporting for tips on what information to include.