I have a Fedora 20 64-bit installation that has a problem when running my 144Hz-capable monitor (BenQ XL2411Z) at 144Hz.
I set it by running 'xrandr -r 144', and the command works (the display is in 144Hz mode, I can feel it) but I get strange flickering windows and graphical artifacts. The flickering is intermittent, and it has a pattern - it seems to be motion-triggered. For example right now, as I type, the flickering rate corresponds to my typing speed. As I stop typing, the flickering rate slows down to the speed of the blinking cursor.
This same monitor works fine on Linux running in 60Hz mode, and in Windows 8.1 in 60 and 144Hz.
Is this a limitation of the open-source Radeon driver? I don't want to try installing fglrx (unless they've improved it since my last attempt).