Only issues with 7970m drivers at the moment is the beta drivers and windows 8, you will lose the ability to control the brightness on Betas only, other than that is a good bang for buck card.
Not experienced this myself. Possible bug?
Not sure, ive got the Vortex 2 and it does not happen on mine. But a lot of people have reported it on here with there machines. A friend with the Vortex 3 has the same issue.