It will be a viable mining choice if Eth doesn't move to Pow which many think it will go to it soon. The power efficiency is a big factor especially at these times where price of 1 Bitcoin is 3500-3800 dollars. I think many miners will see this as a good mining card even if Eth moves to Pow, there are great other algorithms which Nvidia cards do mine well.
Not sure how 350 USD at 160watt TDP is a good deal.
Nvidia is clearly charging you for the Ray tracing on this card which of course isnt needed when mining.
With 350 USD I would rather buy 2 x 1060's (save 30$) and get 48 Mh/s at 220w or settle for 1 x 1070 for 220 USD (save $130) and keep the 31 Mh/s at 120w. And the Polaris cards are even better at this therefore there is no point in buying this card.
Not sure how it performs in X16r but im sure its not that different that it'll warrant buying this over the Pascals.
For gamers its a great deal especially if you have 1080p and want to experience RT - not bad at 1440p either as it will net you 40 fps.