Is this just because its a whole new design or is it normal im sure i have seen reviews done before time using referance boards.
Mactronix
It's rare you see anything more than 3Dmarks and crap-assed unscientific reviews before launch, from either company.
IT could be they aren't as good as the GF8600, or it could be like the HD2900 they don't want a bunch of dip$hits writing reviews on old drivers and then permanently etching in people's minds performance or issues that they may fix around launch. Also remember there was a problem with production that delayed launch and thus do you want people reviewing early flawed parts the way DT did or review launch product?
If you go back far enough you'll see the ONLY time companies leak launches is when they are losing that market. And the $150 market still belongs to the X1950 so why kill those sales when you want to move old product?
Personally I think the HD2600XT(X) GDDR4 model will do well against it's competition, but like the X1950Pro vs GF7900GS you are bound to see some back and forth between the two.
The main killer points will be HD playback acceleration and the how well these games handle the limited DX10 stuff out there now because the GF8600 has no killer DX10 need over an X1950Pro/XT or GF7900GS right now. So can the HD2600XT make it useable? Maybe, maybe not. But like the GF8600 it's likely to lose the DX9 race to the former higher end.