I never heard any enthusiast ever complain an option was power hungry if it was ever beating all other options.
It's only power hungry if the G80 can do the same for less. If it ends up having more features (even on like HDR+AA in the last generation) or more performance, no one will care about the power situation except those who really aren't in the target market anyways.
Big problem will be if there's no advantage, and just that drawback.
Well I think it was a question of production problems, wanting lower RAM prices (the Samsung memory has been shipping since I first learned about it last year and of course dropping prices per card means cheaper MSRP) and then the most important part, no Vista / DX10 pressure, their sales are still doing OK (they actually gained ground on nV during the time they had the GF8800), so better to launch a finished product, than something that is overpriced and not ready for prime time. Don't want a recall-reissue like the GF8800 and the eVGA GF7900s, that costs money and would hurt the brand. AMD is playing is safe, which actually bothers me because it means the pace of competition has slowed.
As for the power and performance, it depends, it's not surprising there's more power, it has more memory than the GF8800, running at a higher bitwidth, and the core runs faster with +/- the same number of transistors (unknown what's inside the core further). So it was never going to equal th GF8800 for power consumption, the question is how much more power and how stable.
But we'll see if it was worth it or not once the performance figures and features list comes out.