I can understand your frustration with Nvidia products holding up.
Look at the past:
GTX 660 is on par with the HD7870
750TI is on par with the HD7850
Now lets fastforward to present day.
The R7 370 is the HD7850... rebranded AGAIN (Like jesus just die pitcairn).
So the HD 7870 is even FASTER now. The 8% clockspeed boost in the R7 370 doesn't explain the performance difference between the HD7850 before and now vs the 750ti. And that's on a MAXWELL architecture. With Kepler?
It gets even WORSE.
Look at the previous graph again at the 760. It was 50% above the HD7850. Now it's 10% above the HD7850 in the form of the R7 370 with the tiny clockspeed boost that got of 8%.
Look, I can sit here and tell you the GTX 660 was a great card, the DATA does NOT HOLD. Kepler fell apart against the HD7000 series.
One final look, look at the 780Ti leading the pack, now look where it is....
But hey, this is why no data was provided to backup the claim that the GTX 660 is a great card. It's just said and hoped that people will believe every Nvidia product is amazing.
Nvidia is GREAT at release, and holds up poorly. I expect the 1070 to blow us away at launch just like the previous Nvidia launches. But unless Nvidia changes something DRASTICALLY, people will remember the last time they were burned with Nvidia performance drops, and start to wisen up. Some people anyway.
The MAJOR problem with the 1070/108 is sit's a refined Maxwell, and if Maxwell isn't holding up, how is refining an architecture that's only getting weaker going to help while AMD is refining an already strong architecture at current games. That's what leads me to be hesitant about a 1070 for ANYONE who holds their GPU more than one generation, or doesn't play Day 1 games, or isn't competitive gaming.