Not sure why anyone would plump for a Vega 64 at the moment - as you alluded to above, performance wise they are competitive with the Founders Edition of the GTX 1080 (from the reviews I've read it's about 70/30 in favour of Nvidia but lets say it's 50/50 for argument sake)......however the 3rd party versions of the GTX 1080 are faster, up to $100 cheaper and run cooler. If the Vega 64 has an introductory price of $499 then they are already too expensive when faster versions of the GTX 1080 are cheaper.

And that's discounting the hype and massive delays of the new architecture and HBM2 VRAM. It's hardly proving to be a new performance benchmark which was effectively the promise 12 months ago. For anyone looking at 'bang for buck' which has always been AMD's strong point, the Vega cards aren't looking like they'll win that battle unless there is some unforeseen magic in an as yet unreleased driver.