First, we'll examine how anti-aliasing and anisotropic filtering affect performance in Quake 3 and UT2003. Again, the highest quality settings were used in both games, but sound was enabled in Quake 3.
Quake 3: Arena
The Radeon 9800 Pro doesn't skip a beat with anisotropic filtering set to 16 samples per pixel, which is very good news considering the drastic improvement to texture quality. Predictably, anti-aliasing is significantly more resource intensive, super-sampling moreso than multi-sampling. MSAA does tend to blur textures more than SSAA, but enabling AF compensates for it. Notice that 2xSSAA cannot be enabled above 1280x1024 and 4xSSAA is limited to 1024x768 and below.
Depending on your settings, there can be a rather large dropoff in performance when MSAA and AF are simultaneously enabled. Quake 3 is still playable at 1600x1200 with 6xMSAA and 16xAF, but you will probably need to reduce the resolution and/or SMOOTHVISION settings to maintain playable framerates in more graphically intensive games.
Unreal Tournament 2003
Again, the UT2003 numbers corroborate the analysis of the Quake 3 results. The graphics engine is much more complex and thus the dropoff is even more massive.