ATI has cleaned up some of the texture filtering quirks from the Radeon 8500, as well. The 9700 can do anistropic filtering up to 16X, and the 9700's anisotropic filtering algorithm is improved.
The best way to show you the effect of anisotropic filtering is with visuals. (Plus, I spent way too much time on edge AA, so this is what you get.) The images below show how higher degrees of anisotropy provide increased texture clarity; anisotropic filtering provides this clarity without aliasing while the image is in motion. The key to anisotropic filtering is taking into account the slope of the surface from the perspective of the viewer. Conventional isotropic mip map filters don't do this, so they have to cut out texture detail in order to reduce aliasing.
If you'd like to see uncompressed versions of these images, go right here. Be warned, however, that the files are rather large.
The Radeon 8500's anisotropic filtering method has a couple of annoying quirks. Its adaptive filtering algorithm acts selectively on certain surfaces, and sometimes, textures aren't filtered as they should be. ATI says the Radeon 9700's anisotropic filtering algorithm better accounts for these polygons, so filtering is applied more thoroughly.
Also, the 8500 couldn't apply anisotropic filtering and trilinear filtering simultaneously. Users were forced to choose between blurry textures with smooth mip map transitions (bilinear + trilinear filtering) or sharp textures with stark mip map transitions (anisotropic). Personally, I couldn't stand playing Serious Sam with anisotropic filtering on a Radeon 8500 for this very reason. That "line" out on the ground in front of me everywhere I went was just too much to take. Ugh.
Happily, the 9700 addresses this quirk, although ATI requires users to check a "quality" radio button in its drivers in order for aniso and trilinear to work together. I'd prefer they do it like everyone else and allow the application settings for trilinear filtering to determine what happens. Nevertheless, the 9700's image output is positively gorgeous. Our screenshots with colored mipmaps show long, smooth trilinear gradients with anisotropic filtering active.
As you might expect, the Radeon 9700's texture filtering performance is excellent, as well.
All told, the Radeon 9700 Pro provides more and better texture antialiasing, at higher frame rates, than anything else on the market.