A few corrections to your post if I may be so pedantic
First off, the 480 is roughly as quick as the 6970 and 570, it's really too close to call, this obviously depends on which websites you frequent and what games you play.
However the 480 has the extra memory and memory bandwidth over the 570, and this can come in handy depending on what resolution you game at.
GTX 480 vs AMD 6970 benchmarks
GTX 480 vs GTX 570 benchmarks
Secondly, the 480 is actually more power hungry than the 580 believe it or not, so it therefore takes the award of "most power hungry single GPU video card".
Link for above info
here
Thirdly, the Gigabyte 480 SOC and SE models which everyone's talking about are not hot or loud running due to Gigabytes custom cooler,
they're actually considerably quieter than a stock 480 and 6970.
Link for above info
here
Fourthly, unfortunately for AMD their driver team is nowhere near the same size as Nvidias,
there's also considerably more games in Nvidias "The way it's meant to be played" program than there is in AMDs "Gaming evolved"
Link to Nvidia TWIMTBP list of games
Link to AMDs Gaming evolved list.
This obviously means that a Nvidia video card owner will potentially have less issues in less games.
You see it all the time on these very forums, people with AMD video cards constantly asking when's this going to be fixed, why doesn't such and such work?
I'm not saying that Nvidia doesn't have any issues at all because they do,
but what I am saying is there seems to be a disproportionate amount of people with AMD problems compared to those who use Nvidia, especially when you consider the below pie chart.
Taken from the
Steam hardware survey
Now I don't want to come across as a raging fanboy but taking all of the above into consideration (barring of course the power usage) plus the added benefits of PhysX, CUDA,
and immeasurably better 3D implementation you've gotta ask yourself why anyone in their right mind would you choose a 6950/6970 over the 480 at its current price?
I guess you could argue that Eyefinity may seal the deal, but seriously you'd want a couple of high end cards to run 3x 1080p monitors and maintain decent fps surely?
And if that's the case then Nvidias surround solution is arguably as good as AMDs?
To conclude, The only reason I can see why somebody would take a 6950/6970 over the 480 that is currently on offer is because their PSU isn't up to the task, plain and simple