I overclocked my EVGA GTX 780 "FTW" edition to 1100Mhz core clock (120+Mhz) and I got crash to desktop for the first time. I got microstutter (possibly V-ram issues) in an open filed, and the game froze when I loaded the save file after I died--the loading screen froze while I can hear/play in the background.
I will test it further and see how stable it is. I might stay on 120+MHZ overclock, or set it to 110 if I got more issues. The game is stable in Unigine Heaven though; it only crashed when I went to 130Mhz.
So is locking the framerate the way to go for this game? I noticed really smooth gameplay when its locked, and crazy stuttering with unlimited framerate. It's kind of weird that the game behaves that when when the framerate goes higher than 60.
Run it in borderless and set max pre-rendered frames to 1 or 2 in the control panel of your graphics card. You can also turn Hardware cursor OFF, decrease the mouse sensitivity, then set Hardware cursor to on again if you hate mouse acceleration; hell, you can even use it with lowered sensitivity if you want. Locking the framerate will also help to some extent, but I don't use it.