The card that will replace the GeForce GTX 680 is not the GTX 770, but the GTX 780. Nevertheless, as benchmarks have just proved, this hasn't stopped GTX 770 from outdoing the 680 as well.
As revealed by Chiphell, the GTX 770 was quite thoroughly benchmarked.
We don't know exactly what model of the card was used in the test, if it was the reference adapter or some OEM version.
The overclocker did push the 2 GB of GDDr5 memory to 7 GHz though, and theorized that 8 GHz should be simple enough to enable as well.
The GPU, meanwhile, worked at 1059 / 1176 MHz (base/boost).
Compared to GTX 680 in tests, the GTX 770 did between 7.4% and 12.6% better. With seven games and benchmarks, that leads to an average of 11.4%.
GeForce GTX 770 Tests Result in Benchmark Score List
The card was compared to GTX 680 and did 11.4% better on average
... so hot right now