For those who are jumping because AMD 6990 is faster and 590 is blowing up:
amd 99% gpu load - Google Search
6990 might be good gpu but the drivers are just crap, once you buy it you'll waste 1/3rd of your gaming time troubleshooting drivers, cheers.
PS: nVidia 590 might have issues but other 5/4 series cards don't, all AMD gpus(5xxx, 6xxx) suffer from this bug, this bug was apparently rectified for 6xxx series but success isn't 100% guaranteed, and the issue is not even admitted for 5xxx users.
Some more bugs(still not fixed, existed for months now):
amd mouse cursor lag corner - Google Search
I'm just tired of issues like this, I'll rather not oc than waste time on changing drivers etc.