Useless. Partners already have higher clocked 7970. 1GHz will not surpass the 680 while consuming more W than the reference 7970. All the reviews declared the 680 a winner, the game is over at the top so this will not change anything from a marketing and reputation point of view.
I'm not trying to say that the 680 is (much) better than the 7970 but that is the verdict.
What might be with this GHz edition is that they know the 670 will compete directly with the 925 Mhz 7970 and they have to break clear. This is just a supposition because I really don't see a point of a higher clocked 7970 by AMD.
GK104 in any shape and form is better than Tahiti and Pitcairn but AMD has the 7850 and if they price it competitively the 7870 in a space were NV has nothing. Of course availability for NV products is a big question right now.