Photos of them haven't exactly been in that great an abundance, and neither were the specifications known in full, or for certain. At least not for the GTX 770.
The card really is powered by a new GK104 GPU, called GK104-425, featuring 1536 CUDA cores.
The board also has 2 GB of GDDR5 VRAM, working over an interface of 256 bits. The clock speeds are still unknown.
Compared to GTX 680, GTX 770 should be 5-10% faster. The price will be lower though, near that of the GTX 670, at $399 / €399 to $449 / €449.