Yes i checked it. it working fine. i play NFS undercover and it is working smoothly.
I install Ubuntu on my i5 it working fine but i faced some problem for driver but now its working fine.

Today's every gigabyte motherboards have undervolting options. I dont think ASUS is good motherboard. because i faced some problem in my old motherboard so in the new pc i install gigabyte. good motherboard i not faced any problem yet.

I dont think it help you to power consumption.
because it is just for keep cool your CPU so there are not any consult power consumption to heat sink cooler.