Have a 780 looking at 1070. But not sure it's worth it.
I reckon it will be worth the upgrade. Time will tell.

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Have a 780 looking at 1070. But not sure it's worth it.
No it isn't... they're doing the same thing that they did with the last two generations because they're so far ahead of ATi/AMD.
GTX670/680 = mid-range / mobile version of GTX780Ti / Titan
GTX970/980 = mid-range / mobile version of GTX980Ti / Titan X
GTX1070/1080 = mid-range / mobile version of GTX1080Ti / Titan 1080
You can get a vague idea of the real full-size chip from the Tesla announcement:
http://www.anandtech.com/show/10222/nvidia-announces-tesla-p100-accelerator-pascal-power-for-hpc
Expect a 25-40% performance bump over the 1080 and 16GB memory for the new titan... probably 12 for the Ti.
I'll pass, should get another year at least from my 980Ti. Look forward to seeing some of these break 2ghz though!