Nikkor, I too have the Extreme4. Have you tried the 1.90 BIOS update yet? Mine came with 1.30, which is what I am running. I had read where 1.70 gave someone an issue with the GTX560Ti video card when I ordered my MB. I had also ordered that same video card. By the time I received my MB, ASRock had pulled 1.70 and replaced with with 1.80. I thought great, so I installed it (couldn't get the flash to work, so used the windows installer). What I found with 1.80 and the GTX560Ti was, I could not complete the WEI with the processor OC'd to anything higher than 4.2Ghz. I went back to 1.30 (I've read where 1.40 is great as well), and was back to having no issues with anything with a OC setting to 4.6 GHz, with my i7-2600k. I haven't tried higher than that.
I see some interesting description comments to the 1.90 BIOS, but I'm not sure what they pertain too.
BTW, I also have on the way, this P8H77-V MB. I needed to upgrade the CPU in one of my boys computers and with the current special on this board and the i3-2120, it was too hard to pass up, regardless of no overclocking, which that CPU doesn't allow anyways.
Performance wise, I find the Extreme4 to be right on par with the Sabertooth Z77. I have both, each running the i7-2600K.