AMD had released the Radeon HD 7970 Ghz Edition a little while ago, replacing the 7970 and becoming the top of the line of AMD.
However, its specs are identical to the 7970; some people managed to flash the 7970’s BIOS with the Ghz edition’s one so as to speed it up, resulting in similar performance.
The 7970 Ghz Edition did perform much better than the 7970 when compared to the 680(GTX), and beat it quite often. In many cases, it was only beaten in performance by the 590 (two processors), the 680 SLI, and sometimes the 6990 (also double). Even in games with the highest settings (like Batman, BF3) on 2560 x 1600 sizes, it passed with flying colors: there were FPSs of about 50 (on a very comfortable system). This is already smooth for a game, let alone the graphics details and the monitor size.
The 7970 Ghz edition is not cheap by any means; it is a whopping $500, compared to the 7970 (regular)’s $430 (USD). So it could be possible to save money by trying to overclock a regular 7970, though it might not be covered by warranty should it overheat and die sooner.
Overall, the 7970 Ghz Edition seems to be the best single-processor card around. It is very possible that AMD was keeping this up their sleeve until after Nvidia released their competitor, the GTX 680.