To sum up:
Haswell reviews determined that motherboards have absolutely no impact on how well your CPU will overclock. People are getting a max of 4.6-4.8 Ghz with the "K" series Haswell cpu's, and it doesn't matter if they are using a 400 dollar ASUS ROG board or a cheap H87 Gigabyte one.
Intel wants enthusiasts to spend the extra coin and buy the Z87 boards which are 2-3X more expensive and are pushing an update that will patch overclocking on all non Z motherboards.







