Other than the DPM bug which on AMDGPU-Pro, seems to only impact my monitor that's on the Active DisplayPort to DVI adapter, my experience is starting to get half decent. I started using some repos with bleeding edge LLVM and Mesa. KSP now runs flawlessly, as does Castle Story. TF2 isn't perfect but, it's definitely more playable than it was before. Cities: Skylines doesn't seem to be any better though but, I think there is a pretty big CPU bottleneck there. Civ 5 runs well until you can see most of them map but, the amount of time it takes to end a turn seems to be faster in Linux but, that could just be placebo effect.
I think my experience would probably be a lot better if I wasn't running 3 monitors though (not across all 3 of course but, just simply using 3.) The third one on the active display port adapter seems to be problematic occasionally although, it's probably just the adapter acting up but, most of the time I don't notice it.