Since upgrading HWE from -lts-saucy to -lts-trusty, I have had recurring graphical glitches on screen, with short black horizontal lines appearing briefly on screen (on top of normal contents), particularly when switching between applications. The lines appear only for a few 100 ms before going away (just enough to register in your eye that there’s something there), so I’ve been trying to make a screen recording to capture it, but of course the phenomenon goes away when I do (perhaps RecordMyDesktop does something with the screen that makes it less likely to appear).
I have another 12.04 system with desktop Radeon graphics, and there -lts-trusty has not produced this issue so far (the one with the issue and the one I’m attaching the logs here from has Intel).
I don’t recall seeing this with -lts-saucy or other previous Xorg packages. It was so obvious right after upgrading that either it never occurred before or was so rare or quick to flash away that it didn’t register.