Texture filtering quality
Here's a sample scene from Serious Sam, grabbed in Direct3D mode, that shows texture filtering in action along the wall, the floor, and on the inclined surface between the two.

Trilinear filtering - Radeon 9800 XT

Trilinear filtering - Radeon X800 XT

Trilinear filtering - GeForce 6800 Ultra - 60.72 drivers - Optimizations disabled

Trilinear filtering - GeForce 6800 Ultra - 61.11 drivers - Optimizations disabled

Trilinear filtering - GeForce 6800 Ultra - 60.72 drivers - Optimizations enabled

Trilinear filtering - GeForce FX 5950 Ultra

The difference between "brilinear" filtering and true trilinear is difficult to detect with a static screenshot and the naked eye—at least, it is for me. Remember that the GeForce FX 5950 is doing "brilinear" filtering in all cases.