Depends. Do you think AMD will finalise a fully working and optimized driver 7970m in the future? Hardware wise, the 7970m is very good. However, the driver is bugging me and I am waiting for a release that will fix the problem.
I would not say the 680m is superior as it falls behind significantly in professional applications. The 7970m is not to far behind in gaming either, the one thing the 680m has is efficiency. The 680m consumes less power and produces less heat.
So is the 680m premium over the 7970m worth it?? Absolutely not!