Has everyone forgotten 2 things:
1) The "Radeon 7900" series is more than 1 card.
2) The GTX560Ti was almost on par with the HD6950.
3) You would hope that it's close to the 7900 series with a 225w TDP if true.
(4) It may have performance "on the level" in a select few situations. Depends on whether we're looking at marketing speak or "real" speak.
Here's an example:
http://www.guru3d.com/article/radeon-hd-6950-1gb-vs-geforce-gtx-560-ti-review/8
GTX560 Ti beats the HD6950 at 1280x1024 but loses by a reasonable margin at 2560x1600. Marketing speak would allow BOTH manufacturers to claim their card is the faster of the two)
5) WHO GIVES A SHIT?
All I care about is how much performance I get for my money. If it's "on par" and costs $50 more, I don't give a damn where on NV's "scale" it is.
If it's "on par", or even a bit slower, but $100+ less, then it's an easy sale and ends up being good for the consumer.
I would anticipate that the majority of people here have a set budget, it may be a high budget, but it's a budget.
Sure, some people can (and do) buy triple GTX580s or triple HD7970s, but most people have $x to spend. If the GTX680 (or whatever) means I get more performance for my $x, I don't care whether it's the bottom card or the top card. Much like I don't care if AMD's top card is half the performance of NV's top card. If NV's top card costs $2x and AMDs costs $x, then I'm going to pick between NV's $x priced card and AMD's $x priced card, not between NV's top card and AMD's top card.