I've started to experience BIG problems with my Asus PG279Q (connected by display port on my MSI Gaming X trio 1080ti):
1) If I set the Hz of the display it does not match with the real Hz, that's: Setting 144hz or 165hz and the game shows like a uggly 60hz, to check it I tested my real refresh rate on
https://www.testufo.com and It show 60hz. Nothing I can do except rebooting the display (check off / on / off the OSD OC 165hz option) and cross your fingers ... not always runs...
As you can see on the screenshoot I also try to downgrade to 398.11 Nvidia drivers but nothing fix the problems...

SHOW BIG SCREENSHOT>>>
https://image.ibb.co/jTHJiT/IMG_0522.jpg2) Turbo button to change 60/120/144 / 165hz does not run as you can see in the link below:
https://youtu.be/hkMSyU4okz8PD: I've installed the last Asus PG279Q officials drivers:
Versión -2015/09/0832.9 MBytes
PG279 WHQL Driver