HardCoreWare recently reviewed the Gigabyte Z87X-UD4H motherboard with a focus on its overclocking capabilities. Back in August, our very own Morry reviewed the Gigabyte Z87X-OC Force and used it to overclock his Haswell processor to about 4.6 GHz with liquid cooling. This is actually pretty high. HCW notes how many people cannot get Haswell past about 4.4 GHz due to how its heat scales with voltage and frequency after you leave its comfort zone.
Image Credit: HCW
According to the review, the new Gigabyte board can get within 100 MHz (around 4.5 GHz) of Morry using just its default "Extreme" setting. With advanced settings, Carl Nelson was able to push it to almost 4.8 GHz on an air cooler from Noctua. This was apparently the highest he has ever seen this CPU reach and maintain stability at.
Gigabyte apparently did some effective tweaks with this motherboard. If interested, you should check out the original review for more details.