Manufacturers and other vendors cheating on benchmarks is nothing new. Intel, AMD, nVidia, ATI, Matrox and many others have been found guilty in whole or part of this in the past. Lately, it seems, the GeForce 7800 Series, a hot item all across the board, has been doing some tricky things to bump up benchmark results. It seems in certain scenarios, even if the user enables 16 x AF, the card will still use 2 x AF for certain portions of rendering, resulting in a poorer image quality. There are also issues with shimmering textures. On nVidia's behalf, they have stated that these are bugs in the driver software, and that bug fixes for some are already in place and others are being worked on.
“We have isolated the problem and we are working on the fix. We will also be working on a fix for the application profile problems that some users were experiencing. We hope to have a fix soon,”
How much of this was actually a bug and how much of it was plain intention to mislead probably won't ever be known, but it is just another reminder of how one should not put all of your faith into benchmarks.