My personal experience in the ASRock Z68 Extreme4 are absolutely smoothly. The memory timings were recognized by the BIOS immediately and correctly set. In operation, the modules run absolutely stable and without abnormalities - so how the just wishes. For the quantitative performance I can not say very much, till it that the chip graphics of i5-2500K (HD3000) in games now slightly better than performs with the previously built DDR3-1333 modules (also Kingston ValueRAM, CL9).
You can not go far wrong with these modules: Conclusion. Who is looking for trouble-free memory without over-clocking and configuration orgies, will find it here.