The site isn't sure when the NDA for the reviews expires but heard that in terms of performance, the GeForce GTX 1070 is nearly on par with the GeForce GTX 980 Ti.
One strange thing though is that the TDP of the Founders Edition is locked at 112% of the reference specification. The reason for this is unknown.
However I recommend waiting for custom cards based on GP104-200 silicon, as Founders Edition is currently locked at 112% TDP for no particular reason. That said overclocking is limited to 1980-2050 MHz. If such power limit is applied to all GTX 1070 cards, then I think this is a very dirty and unnecessary move from NVIDIA to limit GTX 1070 performance. Unlike GTX 1080, GTX 1070 still has a lot of headroom in available power coming from single 8pin power connector.