I'm testing 16.7.2 today with a Radeon HD 7850 and 3 monitors on Win 8.1.
My left and right monitors are Dell 2001FP monitors turned up 90 degrees, and the center monitor is a Dell U3014. This has worked flawlessly with ATI drivers 16.3.2 and earlier.
Incredibly, after the driver install, the central monitor just failed to come online, and one of the side monitors became the primary. This of course messed up all my icons. I was able to get the desktop to display on the center monitor by power-clearing it.
I thought, gee, maybe this is a one time thing, but no - a reboot after getting everything straightened out again left me with the Windows logon screen on my left monitor (normally it's on the center one), and the center monitor just in "power saving" mode. Fortunately, a power cycle of my center monitor regained function again. Since I did it before logging on, my desktop icons didn't need to be rearranged. Again.
This never happened with 16.3.2.
What do I have to configure in the 16.7 drivers in order for my desktop to just come up on the same monitors it was working on when I shut the system down?