I've finally managed to get a hold on Vega several days ago. The card in question is Asus ROG Strix 64. First I tried this card on the blockchain driver Beta, and the system was falling apart. But I booted right after removing my previous 480 GPU. So I DDU'd the driver a couple of times with the same results. Horrible glitches, after completing the tests, even followed by system crashes sometimes. I was about to return the card, but I gave it a benefit of the doubt, so I installed the latest Adrenalin driver 17.12.2. It solved these problems.
However, I'm still getting weird glitching sometimes, after exiting some games. It happened 2 times after sessions in Dawn of War 3 (but not after every session), and now after exiting Team Fortress 2. Didn't after some other games, like DE MD, RotTR,, Hitman, and such. First time it disappeared on its own, the other two times I had to restart. It doesn't matter if the HBCC or Enhanced sync are enabled. But Freesync is on. I also didn't experience this with my previous 480 GPU, and a 390 before it. Here's how it looks like:
The rest of the specs is: 1800X, 2x16GB of RAM, and the Windows 10 pro 64-bit, with the latest updates. Its all on factory settings, not OC-ed.