Given the lack of impact of the Vega launch on the high end segment pricing, cryptocurrency mining, and the likely impending rise of GDDR5 prices, I think $660 for a quality OEM 1080 Ti is a pretty good deal these days. Includes shipping.
Just grabbed one myself.
The catch is that it's Mass Drop. But I've not had issues personally on the couple drops I've participated in over the past year or 2. And I live in Canada. The only obvious caveat is that it's not slated to ship for 3 to 4 weeks.
Edit: I'm sure TR readers are savvy enough to pick this up, but FYI, this is not the XTREME edition that was reviewed at TR, but the "vanilla" edition. As specs go vs the Xtreme, the back plate is a bit different (logo and smaller copper back piece) and the stock max boost clock is about 40 Mhz lower. I believe the board design and power delivery circuitry, etc, are identical. I personally doubt there will be much of a perceptible difference, if any, in actual use.