If you're one of the ones still having problems with this board getting it to post, try another couple of things I needed to do to get mine to post (after many hours of buggering around... not too impressed with this asus so far)
In addition to Gibbo's sticky - be very careful with OC tuner or ANY auto settings, when i eventually got mine to boot I saw some pretty scary voltages (at least in comparison to what i'd set), I think the board was trying to compensate for vdroop and jumping way over any manual settings.
I've got a 2600k and Corsair XMS3 btw
First - Disable EPU via the switch on the top right near the dimm sockets it should be in the UP position and NO blue LED by the switch should be lit on power up.
Second - Enable TPU via the switch bottom right underneath the PCI/PCI-E slots, blue LED should be lit on this one.
Unplug the power cord and clear the CMOS.
Give it a few seconds, cross your fingers, power on and hope for the best. At this point mine posted, quickly take the chance to go into the EFIBios and manually set the voltages to stock.
Once you've got windows up and running update to 1053 Bios using the Asus update app, mine wouldnt update from the bios utility, maybe an issue with the 0402 bios dated october last year...
Mine has then remained stable since - I have started to push mine a little, but only a tad at time, still perfectly stable, currently at 1.235 4.3Ghz
Follow Gibbos voltage guidelines, espescially memory voltages my XMS3 is perfectly happy at 1600mhz 9-9-9-24 with 1.5v and has greatly improved stability of the CPU at lower voltages ?! dont know why. Anyway hope that someone else is able to get round thier issues like I was, the asus board nearly took the quick way to my front garden last night.