The new set of nVIDIA dirvers (91.47) allow Transparency AA on GeForce6’s, which was exculsive to the GeForce7’s previously.  Elite Bastards explains what exactly this type of AA does, and it’s effects on gaming.
“One of the major caveats of current multi-sample anti-aliasing implementations however, is that is cannot deal with alpha textures, which are often used for items such as chain-link fences, leaves and the like. This means that while the rest of the scene is nicely anti-aliased, any alpha textures remain in their usual, ‘jaggy’ state.

To combat this problem, both ATI and NVIDIA have recently introduced technology which can pick out alpha textures in a scene, and apply anti-aliasing to said items. In ATI’s case, this is currently achieved only by performing super-sampling on alpha textures (although a multi-sampling based method will be added to ATI’s drivers shortly), whereas NVIDIA’s GeForce 7 series has the ability to perform either multi-sampling or super-sampling to alpha textures. It is this very ability (dubbed Transparency Anti-aliasing) that the GeForce 6 series have inherited circa ForceWare 91.47.”

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