Anybody else had scary problems while trying to update the AMD display driver to the new Boot Camp version (on the Retina iMac w/M295X)? I did it on my 8.1 Boot Camp install last night, and the install seemed to run OK, but then after reboot, Windows hung on a dead screen at startup (not just black, but with the display completely turned off). I went through a bunch of reboots, some of which took me to the Win8.1 recovery tools menu (but couldn't find anything to fix), and some of which went back to the dead screen. Then the fan started ramping up to max, and when I rebooted into OSX, I found that iStatMenus wasn't getting a reading for the GPU Diode temperature sensor. I wound up shutting down altogether and doing SMC and PRAM resets, which eventually got my temperature readings back in OSX, but after that Windows failed to boot altogether, coming up with a screen about BCD and EFI errors and wanting me to repair it from installation media.
Since I'm very leery of letting Windows mess with the Mac boot environment, I eventually decided to just remove the partition with Boot Camp Assistant. Then I created a brand new USB installer from ISO with the BC drivers and recreated the Windows partition (all using BCA), and did a fresh install of Win 8.1. Everything went in smoothly this time (there was a message that the Boot Camp installer had stopped working, but everything seems to have gotten installed OK), and now I'm up and running on the current BC drivers, display and all.
Alien Isolation's prettier than ever now that Depth of Field is working, and seems like it's running as smoothly now at 2160p as it did before at 3200x1800, so I guess I can't complain. A thoroughly alarming process, though.