I am using R9 390 Gigabyte G1 version and my experience with it so far is great, i tried all latest games with ultra settings and card runs them smooth as silk. Games worth mentioning are
GTA V
Batman: Arkham Knight (mind you its nvidia optimized still runs it on ultra without any issue :tv
The Witcher III
All future games require heavy VRAM, also DX12 these two were the selling points for me to buy AMD, I am not a fanboy i just want best bang for my buck. Go for nvidia if youre prone to that but keep all aspects in your mind before making the
purchase. GOOD LUCK