Intel's 22-nm process allows Ivy Bridge to consume much less power than its predecessor when running at the same speed. The 3D transistors purportedly offer better performance at low voltages, which is great for mobile applications but perhaps not ideal for overclocked desktop rigs. That said, I'm reasonably impressed with how well Ivy overclocks. The Core i7-3770K was stable at 4.4-4.5GHz without so much as an extra millivolt applied to the CPU. Those speeds only increased system power consumption by a modest amount, so there's no need to invest in an aggressive cooling solution. With our single-fan Frio config, CPU temperatures were in the 50-60°C range under load.
Moving beyond 4.5GHz requires additional voltage, and that's when Ivy really starts to heat up. With the CPU voltage increased to a seemingly conservative 1.35V, system power consumption soared, and thermal throttling reared its ugly head. We'd recommend liquid cooling to keep high temperatures (and the associated throttling) at bay when approaching 5GHz. Even at 4.8-4.9GHz, with both of the Frio's fans installed, our CPU eclipsed 90°C with regularity. Although we've only overclocked one Ivy Bridge CPU, our findings jibe with what we've been hearing from the motherboard makers.
Our Core i7-3770K hit similar limits on all four boards. The Asus was the only one stable at 4.9GHz, but the others were only 100MHz behind. At stock voltage, the Intel and MSI boards both managed 4.5GHz, while the other two topped out at 4.4GHz. You should be able to get a good overclock out of any of the boards we've tested. The experience is the only thing that will differ substantially.
Of all the boards, the Asus P8Z77-V offers the most enjoyable overclocking experience The firmware is easy to use, and the accompanying Windows software is the best in the business by far. If only Asus didn't insist on an unseemly "multicore enhancement" that overclocks the CPU without the user's permission.
Gigabyte plays a similar trick with the Z77X-UD3H, and its implementation is even sneakier. The auto-overclocking software is too aggressive, as well, and the EasyTune Windows utility is overdue for an update. That said, Gigabyte's new firmware makes manual overclocking easy. I'd love to see the interface ported to Windows, where it would be a step up from EasyTune and the accompanying 3D Power app.
Then again, MSI's Windows-based ClickBIOS implementation is painfully slow on the Z77A-GD65. The Control Center app is snappier, but the voltage adjustments didn't work properly for us. Fortunately, the firmware interface is solid. The ability to define a custom profile for the OC Genie button is a particularly nice touch.
OC Genie is the easiest auto-overclocking scheme around, but there's merit to Intel's hybrid approach, which let us take the CPU up to 4.5GHz by dragging a single slider on the main firmware screen. The DZ77GA-70K can handle manual overclocking, too, and Intel's firmware and Windows utility both offer a good user experience without any niggling issues. They're a little short on options compared to the equivalent Asus offerings, though.
Since all the boards reached similar clock speeds, I'd be hesitant to decide between them based on the overclocking experience alone. Ideally, you're only going to be overclocking the CPU once. And I'd recommend it. Ivy Bridge appears to have a decent amount of "free" clock speed headroom—and even more if your cooler is up to the challenge.