On the one hand, it's probably like Rollo says: the drivers' immaturity is the main culprit behind the lackluster performance with the GX in those benchmarks. Nvidia certainly seems stupid with the way they've been doing things lately, but you can bet that they're not so stupid that they'd put a card on the market for $600 that didn't beat the closest competition. The difference likely won't be too big, but you can be sure they have built a card that is faster than any single-slot card on the market. I know it's hard to give them anything - especially $600 for a card that seemingly does nothing more a much cheaper 3870x2 - but give them credit for being smart enough to know that at least they need to make a faster card - in all environments - than a 3870x2.
Unfortunately, for a company as smart as Nvidia should be/has been, it has made some rather grievous errors this time around in not having adequate drivers ready. It's as someone else said in this thread - what the hell has Nvidia been doing all this time? You would think that the time they saved in not developing next-gen technology would have at least given them time to develop a decent set of drivers for their decidedly not-next-gen technology. Had they had drivers ready earlier, they would have been available for those inevitable pre-release reviews that Tweaktown, etc. are famous for, and thus could have avoided the debacle that this release is turning into. I don't see how Nvidia has anyone to blame but themselves. If they want people to believe that they have a fast card, then have your drivers ready, lift the goddamned NDA and let people talk about it, let people do their own benchmarks, and quit being a bunch of corporate George Bushes about everything. That's how you save face, gain back market share, and make more money for your stockholders (the only thing Nvidia seemingly cares about).