The ATI fglrx driver I run against my ATI RS690 chip in my dualhead setup definitely has its quirks. When resuming from disk, both monitors must be turned on when I press the computer's power button, or the X server will behave very odd.

Hard to describe what happens, but when moving the mouse, the whole desktop image is moved instead of only the mouse pointer.

Hardware! I hate hardware! I want all of it to be emulated in software.