http://wccftech.com/gtx-1070-1920-cuda-cores/Looks like this will be the card to buy for best bang/$. By far. Very close to the 1080 performance, and at 379$ vs the 699$ for the 1080 coming out in 10 days, it's a huge, huge bargain. IMO 1070 SLI will be a very effective option, basically 50$ more than the founders edition card for the 1080 (nobody knows when the 599$ ref card will come out, and all the other brands will have higher pricing than that, with various options and doo dads, so 699$ for the founders/etc is a more realistic 1080 price).
Lots of reviews out today now that the NDA is lifted on the 1080 - pretty good performance across the board, and it is indeed faster than 980sli in many, many tests (not all, but most), and is a good 30 to 50% faster than the 980ti/Titan in many as well. Well worth it. Also, a TON less power drawn, which means less heat. This opens up a lot of options too in terms of power supplies.
Still, the 1070 I think will be a huge seller. While I'm planning on getting 2 1080s right out of the gate in a couple weeks or less, I'm also going to grab a 1070 out of interests sake, and build a mini/micro system with that card and some leftover parts (need to pick a small case still). Titan performance out of a 379$ card. Great for VR users, big time. Also, the reason I bring up 1070SLI as a great option is that many players here run 3 screen (HTC has said as much as well based on their data). Nvidia has really improved how surround/3screen works and looks, and having 2 1070s will allow 3 screen users to truly push their panels to max performance/fps IMO, for a price not much more than a single 1080.
