Intel X79 Core i7 4960X Review
With the reduction in die size and shrink from 32nm of the Sandy Bridge-E down to the 22nm of the Ivy Bridge-E there is a massive difference in temperatures at stock. 12°C at idle and 8°C under loading is an enormous improvement. The idle temperature of the overclock is similarly 8°C cooler, although the load temperature is the same because we always overclock as far as we can.
It's not only in thermal output that the i7-4960X is more efficient, as it draws significantly less Watts at the wall when compared to an identical system with the i7-3960X in it. This will save you a fortune in electricity if you have your system on for a reasonable amount of time a day.