Regarding the Catalyst performance gains that were discovered in 3D Mark 2003 ATi has responded with the following:
[COLOR=royalblue]The 1.9% performance gain comes from optimization of the 2 DX9 shaders (water & sky) in Game Test 4. We render the scene exactly as intended by Futuremark, in full-precision floating point. Our shaders are mathematically & functionally identical to Futuremark's & there are no visual artifacts; we simply shuffle instructions to take advantage of our architecture. These are exactly the sort of optimizations that work in games to improve frame rates without reducing image quality & as such, are a realistic approach to a benchmark intended to measure in-game performance. However, we recognize that these can be used by some people to call into question the legitimacy of benchmark results, & so we are removing them from our driver as soon as is physically possible. We expect them to be gone by the next release of CATALYST.[/COLOR]

Meanwhile NVIDIA says the following regarding Futuremarks findings:
[COLOR=royalblue]Since Nvidia is not part of the Futuremark beta program (a program which costs of hundreds of thousands of dollars to participate in), we do not get a chance to work with Futuremark on writing the shaders like we would with a real applications developer.[/COLOR]

Draw your own conclusions to these reponses.