There a piece here from Corsair about possible psu compatibility issues, due to C7 sleep state drops power consumption by so much--down to as little as 0.05a--that some power supplies aren't compatible.
http://www.tweaktown.com/news/30310/corsair-talks-haswell-power-supply-compatibility/index.html
http://www.tweaktown.com/news/30310/corsair-talks-haswell-power-supply-compatibility/index.html