Ok I have some info that mightve been posted in this thread.. this is from a Chinese friend of mine who has been researching these cards with info from Chinamen who dont care about NDAs.
I'm not sure what has and hasnt been posted here, but i gathered up all my info to be concise here for the OP to either add or not-
G80
-GTS same length as the 7900GTX
-GTX is longer
-FEAR 1600x1200: 16xAA @34FPS, 4x/8x @80FPS, No IQ options @130FPS
(for reference 16x12 no AA/AF, X1950 Xfire is 124, 7900GTX SLI gets 139FPS)
-Vastly improved HDR performance
-A64 4000+ 3dmark06 9K
-C2Quadro 3dmark06 12K
-Black PCB for retail G80s
-Have 512b MC on all G80s, but its disabled because GDDR4 is largely unavailable
-Nvidia might respin G80 on R600 launch to enable the full 512bit MC on R600 launch if needed
-The NV10 chip to the side of the main GPU is a 10bit/27mhz video DAC (possibly H.264 decoding)
-$699 possible pricetag
G81
-June '07
-65nm
-GDDR4
-512bit MC
ATI R600
-This is ATIs last attempt, so its going to be good. And thats why they dont care about missing Christmas sales.. its the last from them like this (high end). After this, everything moves to a pro-AMD stance.
-16 layer PCB
-512bit MC
-8 Memory channels
-GDDR4
-Extremely hot (but AMD is helping with that big time currently)
-80nm
-Produced by TSMC
All in all-
R600 will be a beast, but might not destroy G80 in performance regardless.. should be a very good match or beat G80, but as stated above, NV is thinking of respinning G80 on R600 launch if needed (to enable the full 512bit MC + GDDR4).. and G81 will be ready in June. Its not looking good for "ati" high end in the future, Nvidia wants to punish ATI one last time to end this charade once and for all now that AMD took over ATI.
My thoughts-
I'm extremely happy if this info is all true, and I'm inclined to believe it since its from China. People in the west fake leaks because they cant get any info out of any NDA signees.
X1950 Crossfire / 7900GTX SLI performance on a single card +DX10/SM4, faster HDR, HDR+AA on Nvidia with Nvidia driver support, unified shaders.... is all phenomenal and thats what I was hoping for and expecting.
I'm not a big fan of the "waiting game" because its a game you cant really win. I'm buying G80 and buying G81 as well in June. Will skip the respin if Nvidia does that on R600 launch. Then after that I'll be buying G90 as well.
All I've found with the waiting game is that you end up holding your current card for far to long till the value is completely gone from it. Then you have a half worthless card and dont get to play with the newest stuff. So I sold my GTX and am now eagerly awaiting with check card in hand to order the first 8800GTX I can get my hands on.

The value of all current X1900 and GF7s is about to plummet. I lost a total of $40 of the original purchase price of my 7900GTX, which isnt a bad loss IMO.. one of my better "rounds".
I hope for R600 to be a good chip, I really do because I want to see The Final Product be a damn good battle versus the mighty Nvidia.