First, a word of thanks to Omni, rampagedev, and others who have worked to get Power Management working on LGA 2011 boards.
My current rig is a Sabertooth X79 (latest BIOS), 4930k PCU, 32gb 1866 memory (Corsair), EVGA GTX 650 graphics.
I ran solid for about a year using a i7-3820. No stability issues at all. Everything just works. I upgraded to a 4930k a few months ago without much incident. No stability issues at all and again everything just works.
I was excited to see that Apple finally supported Power Management for LGA2011 CPUs in 10.9.2. Following guides by rampagedev (http://rampagedev.wordpress.com/) I was able to get PM up and running, both under Chameleon and Clover. It works using the vanilla AICPUPM kext and an SSDT generated using Pike's script.
However, what's tripped me up has been some stability issues. When I load SSDT I get random restarts. I've tried to pin down the cause using system log but it doesn't seem much help. I've chased a few red herrings (certain applications, sound drivers, etc.) but no matter what I do the crashes persist. Sometimes the restarts are instant, but typically they come after things start to crash -- especially Chrome and Finder.
When I remove the PM SSDT things once again become stable.
I've run memtest and my memory is fine.
I've tried various BIOS settings and as long as I have the PM SSDT loaded, I get the random crashes. It happens on stock settings, overclock settings, etc.
Shilohh suggested I do a CMOS reset, load optimized defaults, and try things out. I'm going to try that now, leaving my 1866-certified RAM at 1600.