I have attempted the upgrade to Windows 10 from 8.1 twice and both times with Catalyst drivers installed Windows thinks my display refresh rate is slightly lower that whatever it is set to. For example, if I set it to 60hz in CCC or the Windows Display settings media players report the display refresh to be 53.38Hz. While running a game with Vsync on, Fraps also reports this lower framerate. This obviously plays havoc with the smoothness of video playback.
I have tried both keeping the Win 8.1 version of the 15.7.1 drivers that are carried forward when I do the upgrade as well as running Display Driver Uninstaller and then installing the Win 10 drivers "clean" and the issue is still present. With only the Microsoft Basic Display drivers installed the display refresh rate is fine.
Under Windows 8.1, everything works fine. I have rolled back for now and will wait to see if this issue is addressed.