So people can SLI this card to have... 6 GBs of video RAM? That's more than I have in regular RAM...
Oh.. and $500+ price point? How fast is that card gonna be overtaken in the next year?
Honestly the whole idea of this card is the dual GPU's and that's beyond insane. I don't know how much heat does this thing generates, but its far better than the 400 and 200 series for sure. Rather than getting two GTX 580's for SLI which would cost like roughly a thousand dollars, you can just go with the GTX 590 (one card) and be worry free about SLI feature.
Anyways, I'm happy with my two GTX 560's. They're incredibly amazing. I run Crysis like cake and chocolate. Dead Space 2, Mafia 2 and other high end games are pretty smooth with those two video cards.
Edit - I forgot to mention, other than PhysX technology, GTX 500 series does bring a new feature to the table which is
Tessellation. Does ATI have this feature?