Remember Carmack said 2 things of note (they may not be related anymore as this title has evolved 8000 times since then proabbly).
1) Carmack said that using the standard path the R9800 was faster than the FX5900series.
So only in the NV3X path did it lead.
2) Carmack has since said that the NV3X path has been dropped.
Which doesn't mean some tweaks haven't be added to help, but it's no longer a fast lane path for NV3X only.
Now this means nothing for the next gen cards, different story, the GF6800 is far different/ahead of the FX series, and should have a much better showing with no compromises.
However for the last generation of cards, expect the R9800 to do fine. And knowing that so many more people will have FXs than GF6xxxs ID likely made it still playable on the FXs, so all the top of the last generation should be just fine.
Also expect some additions from ATI under OGL2.0, but don't expect them to be miracles.
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