Many users have free sync flickering (standard and ultimate engine) on this monitor. The games are for example dota2, witcher 3, age of empires 3 asian dynasties, ut alpha, Tomb Raider ... . Further games can be found here.
I've tested a wide range (until catalyst drivers of August 2015) of AMD drivers. All are flickering.
This monitor has a VA panel. Maybe it needs a special AMD driver implementation. The flickering problem on a certified free sync monitor is very awkward for Samsung and AMD.
So I hope you will release a fix soon.
Used hardware and software:
16 GB DDR4 3200
Gigabyte Z170 Gaming 5
Sapphire R9 Fury Nitro OC
Windows 10 x64
AMD Catalyst 15.7.1 - Crimson 17.3.2