@amd Matt, and everyone else.
When someone reports flickering on Freesync, with Catalyst 15.7 and later, especially Crimson 15.12/16.1 please check your DP cable.
Especially if you have XL2730Z the cable that came with the monitor is not DP1.2 but DP1.1 and you have the flickering because of the cable. Throw it away and buy a good DP1.2 compliant cable. (they are not expensive).
Why I say that. Cutting the story short, I received the refurbished replacement monitor last week from BenQ, straight away had bad vertical flickering experiencing (before it became worse), with my "initial" 2730Z.
However I couldn't test anything else with the 295X2 (has only mDP and a DVI) and when decided that I had to try the DVI and buy an mDP to DP cable, the scaller was gone and the monitor needed replacement.
However this time around I decided to try HDMI with the R9 Nano (flickering was there when received the monitor). With HDMI the screen was crystal clear, and no flickering. (Alas without Freesync)
So ordered a new DP cable which received today.
I put it on, and the screen is perfect, with Freesync on. If I put the cable that came with the BenQ monitor, it only works with Catalyst 15.6. Any other drivers and the screen is flickering badly, especially when Freesync is ON.
Same DP cable used on other non freesync monitor but generic, is fine, and has no issues both with Nvidia & AMD GPUs.
AMDMatt knows my complains about the various Catalyst drivers I have raised in here over the best part of 6 months, compared to the 15.6.
Apparently all issues were down to the cable supplied by BenQ, and possibly destroyed also the scaller needing a monitor replacement.
Matt, since you have access to more people than myself, and you have the time, have a look at it. It will save a lot of grievance to AMD who's not fault the flickering with the 2730Z especially, but to the cable supplied by the manufacturer.