Some games have bad frame drops to the point of making it unplayable, not sure if it was freesync issue but in watchdogs frames dipped to low 40s constantly to the point I just uninstalled it. Even in GTA 5 online, even with freesync off it randomly drops fps to 50s but at that time GPU usage will be very low, it was weird.
But the thing that made me sell was the flickering issue, it flickers randomly even while scrolling in YouTube. It was really bad like I'll be watching a video and scroll down to recommended videos and it'll start flickering. They never fixed it even after reporting it. Now I'm using my old HD 7850 and it doesn't flicker anymore.