I have multiboot both Windows 7 and Windows 10.
Specs are intel core 2 quad overclocked to 3.49Ghz and sapphire hd7770.
Win7 runs 14.16 driver and fps is good.
On Win10 I had a driver update from Win7 14.20 to 15.7.1 which affected performance in games.
For example fps in Cinebench r15 OpenGL test dropped from ~55.5 fps to 16 fps. It reverted back to 51fps after several reboots.
Fps in DotA 2 dropped from ~60 to 24.
Some games like ArmA 2 still run smooth.
Also twitch.tv loads cpu up to 45%