In trying to resolve my no video on cold boot issue, I tried the nVidia Webdriver 10.9.3 drivers and my system froze on boot. I had to boot to my DR clone and remove the boot loader entries that made the nVidia drivers active.
Now I am back on the Apple drivers. On cold boot, my screen immediately goes to sleep mode when it reaches the GUI login screen under 10.9.3 (worked fine on 10.9.2). If I press the hardware reset button, the system boots normally and the GUI login appears as normal. I have the Intel Integrated Graphics already disabled in BIOS. I also changed my system ID from Mac Pro 6,1 to iMac 14,2 as part of my attempt to solve the issue.
I have a GTX 690 (essentially two 680 GPUs on the same card) but it seems like a similar issue.
Anyone else seeing this issue?