Thanks to a "certain" friend of mine who's under the NDA, i've had a quick look at nVidia FTP with pics, "reviewer's guides", drivers an most improtantly a whole plethora of the GTX470/480 benchmarks against the HD5850 and HD5870 and from what i've seen, the GTX480 beats the HD5870 easily by 25% on average. Sometimes it's 10% sometimes 50-60% but the GTX480 always wins.
My initial previsions were correct if this is verified as it completely shades the 5870 and licks 5970's feet. I sincerely doubt this is the case, but if true i'll sell my 5970 in a blink