I OC'd my 950 yesterday. I got it to 4GHz with minimal a minimal voltage increase. It's at 1.28V atm. I initially tried it with 1.35 and the temps were quite high but after backing off the voltage (and tweaking it to improve stability) the temps are 36 idle and 74 load.
I tried turning on Speedstep and Turbo, but that seems to require a decent voltage increase to keep it stable. As with most 950's, it seems they hit 4GHz easily, but require a decent amount of voltage to go beyond the 4GHz mark. But I don't think my current cooling solution is up to the task of the higher voltages. I may move to a Noctua in the near future, and I will consider using it then. But the chip is running well at 4GHz with decent temps and a low voltage, so I'm happy.