GTX 480 draws about 40 more watts than the 7970, let's get back to reality.
The reality of the situation is this is worse than that even... This is a GTX 480 that draws more power, and is slower than the 5870. Can you imagine that?
Because that is what the 7970 is shaping up to be compared to the 680, slower and draws more power.
5xxx wasn't a GPGPU card, and it wasn't even a very good DX11 card. The only reason it looked halfway decent in 2010 is because there weren't any DX11 titles like we have today.
Hence we get back to this root of this discussion. The metrics people were trying to use to discredit 4xx and 5xx cards in favor of AMD cards have been reversed, and it's now the AMD card baring those burdens, while not having the benefit of actually being faster.
The 5870 remains a solid card even today, 2.5 years later. Few games utilize DX11 at all, and the ones that do often don't use it in a way that significantly improves user experience. You can thank consolification of games for that. By the time tessellation is mainstream, we'll be on DX12 anyway.
Regarding power: idle power matters much more than max power if you leave your computer on for much longer than you game. (You need to take a weighted average.) So I think for most normal people, especially those who leave their computers on 24/7 but even just those who write in MS Word/websurf/check email/etc. more than they game, the idle power matters more. I've posted many times about this phenomenon in the past. So it will be interesting to see how the GTX 680 does on idle power.*
As for the 680 vs 7970: GPU boost, adaptive VSync, PhysX, CUDA, different UI, vs. +1 GB VRAM and Dual Bios switch. Both have some fancy anti-aliasing stuff that frankly I don't care about. Possibly different noise characteristics, too. And obviously pricing may be different.
On paper, Nvidia has the better feature set. (I am assuming that Kepler is capable of single-GPU 3+ monitors and if necessary can copy the Dual Bios switch idea.) But the advantage isn't that great in real life since few games use PhysX at all, and the ones that do often don't do it in a way that significantly improves user experience. Sort of like the +1 GB VRAM probably won't help anyone not running 1600p or Eyefinity so it's just "nice to have" but doesn't really help anything. UI and anti-aliasing I guess can be a personal preference thing.
So the real bonus of going NVDA, I think, is GPU Boost and Adaptive VSync.
By the way, there are few bad cards, just bad price points. For example, if AMD had released the HD 5830 at, say, $180, it would have gotten much better reviews. Or if the GTX 480 had been released for $50 less, that would have blunted a lot of the panning re: heat/power.
If the 680 helps drive down prices for 7970 that is good from a consumer standpoint.
* - Incidentally, this is what makes Nvidia's Optimus switching system strong for mobile. Idle power matters more!