There are now many sites with reviews of the upcoming 980x but Hardware Canucks had some interesting overclocking info.
Since this is after all a brand new $999 processor, we self-imposed a 1.35V-ish maximum during our preliminary overclocking sessions with this processor. With the unlocked multipliers overclocking was obviously a breeze, as we could merely increase the CPU multiplier as needed and adjust the BCLK to extract those last few megahertz.
We were fairly satisfied with our results. Yes, you can get similar clocks at similar voltage from an above-average Core i7 D0, but those tend to run exceedingly hot. Our sample ran fairly cool, peaking in the low 70C's during LinX. Furthermore, we suspect that we have a relatively early sample since ours was manufactured in 2009 while all the other i7-980X were made in 2010. Combine this with the fact that Intel's review sample E.S chips are never really great overclockers, and I'm willing to go on a limb and say that the retail processors will be able to achieve a solid 150-200Mhz more than our sample at similar voltage.
LINK TO OC RESULTS