I have a Founder's Edition 1070 and love it. I am coming from SLI'd 970s. To be fair, the 1070 is comparable to the 970s where the game has a good SLI profile. Otherwise, the 1070 is a quantum leap. It is paired with my i5 2500k, which is overclocked from the stock 3.3 ghz to 4.4 ghz.
I am now using it for both my Oculus Rift and with my 4K HDTV at 60hz. I have run many Rift titles so far, including several of my sim racing titles, iRacing, Assetto Corsa and Project CARS and the 1070 easily gives me the need 90 FPS without any significant eye candy compromises.
As far as 4K, the card performs surprisingly well. With 4K, I can turn off AA entirely and that helps with performance. I have run Crysis 3, Dragon Age Inquisition, Forza 6 Apex, Doom, Dying Light, Witcher 3, Call of Duty Black Ops III and Fallout 4 and each game looks amazing at High or Ultra settings with FPS generally averaging 40-60, with only occasional drops into the 30s. I have noticed no slowdown with any title at 4K.
In summary, so long as you pair it with a decent CPU that doesn't bottleneck it, the 1070 is a great option for the Oculus Rift and/ or 4K.