Just want to report that for my use, I've found the Crimson 15.12 driver release completely stable using Windows 8.1 on a Dell Precision Workstation with an ATI Radeon HD 7850.
I never power the system down, though I do have the display driver power down the 3 monitors when the system is not in use. Those monitor power transitions have been flawless, and the system has been running on the bootup needed after the Crimson 15.12 installation for just over 7 days now...
Examples of usage over the past week include running Visual Studio 2015 Update 1, VMware Workstation (with Win 7, 8.1, and 10 VMs), Adobe Photoshop CC and Acrobat, various Office 2010 components, Internet Explorer (including some videos), Windows Media Player, CMD prompts, Beyond Compare, Tortoise Subversion, and many other miscellaneous desktop tools, including some that use OpenGL and sometimes quite a lot of applications at once. Notably I do not run any ridiculous "Modern" Apps, which are all removed from this system, and I don't do any gaming (though I ran the classic Solitaire from Win 7 a few times). Oh, and I have Aero Glass for Win 8.1+ running with an alternate (Aero 7) desktop theme and I use Classic Shell.
Generally speaking I ran the Crimson settings tool a few times at the beginning (including the Additional Settings component that's like the old CCC) then haven't run it since.
Given that I've had absolutely NO problems or glitches in a week's use, I'll say this:
AMD: Nice job making a driver that's nice and stable for serious computer usage.