Of the problems I've read about 1/3rd of the people that believe 320.18 killed their GPU have been unable to get even a picture again (even at POST) to even try and install older drivers, others have managed to roll back fine.
EDIT: Does seem a lot of people are claiming these drivers have "killed" their GPUs as it goes to a black screen soon after booting into windows but when someones managed to persuade them to reinstall older drivers from safemode its all working fine again.
I had the same issue with the black screen when attempting to boot into Windows with these drivers.
My fix was to disable intel HD graphics chip (which shouldnt be active anyways?) through device manager in safe mode. After this I restarted and Windows booted straight up
Maybe this was my system only but it could help others with this issue.