I don't know how to feel about the card until I see official reviews, I think jumping to conclusions is stupid when people start to argue about them.
We can state our opinions, but no point arguing. My opinion is it is a card made to be "awesome" and not necessarily to be the best performer. I think SLI 580's will clock higher than a 590 and the % increase in 580 SLI will come close to the % increase in price it has. Just my assumption.
Card comes out 24'th I believe.
As for the value vs. 580 SLI... you are right that is hard to say. It may be better or worse considering that your chance for getting a meh clocker is double with SLI (buying 2 cards) and the 590 is supposed to be handpicked... but OCing is different for everybody so there is really no argument for either side.
Some people will get a better deal (price per performance) and some won't...