Currently under investigation over at HardOCP: It appears that the Anit-Aliased pictures of NVIDIA's GeForce FX don't do it justice due to the manner in which the AA filters are applied both before and after the frame which is to be painted on the screen has left the frame-buffer. Traditional screen-capturing utilities typically capture images from the frame-buffer, thus neglecting the effect of the latter image-quality-enhancing filters. I'll let the last line of the quote speak for itself. Of course, NVIDIA and the rest of us would like to get to the bottom of this issue.
The GeForceFX's technology applies filters that effect AntiAliasing and Anisotropic filtering before the frame buffer and after the frame has left the frame buffer. In short, this means that all of our screenshots do not accurately represent the true in-game visual quality that the GFFX can and will produce, as the screen shots were pulled from the frame buffer (in the "middle" of the AA process). We have come to conclusions about the GFFX IQ (Image Quality) that may be simply wrong.More information @ HardOCP