NVidia's drivers are far better, and you'll get a card from an independent card manufacturer if you buy Nvidia. So of course Nvidia's site wouldn't say much. If you buy the BFG 6800 for example.. you would have to go to BFG's website.
Because the 6600 GT beats it's ass in every single aspect. The X700 isn't that much better than the X600 and the X600 sucked. In the mid-range area, nVIDIA has got ATI's hands tied. Some people think the X700 as ATI's counterpart of nVIDIA's 6600 GT, but it's far from it.
BTW, sorry about accidentally posting in your post. I clicked the 'Edit' button instead of the 'Quote'.