Something strange going on with my nVidia drivers/control panel (who ya gonna call?).
It's an 8800GT with Forceware 169.21. Individual game profiles have never worked for me - if I choose "use the advanced 3D image settings" and create/modify profiles for games, it gets completely ignored. The same happened with my old GeForce 5900 and a much older Forceware.
So anyway, I set it back to "let the 3D application decide" which works fine for games that have their own AA/AF settings (which is to say, most of them except LFS).
I've just tried the test patch and found that AA and AF were still most definitely on! I had a profile set for LFS forcing AA and AF, which was obviously still being used even though I'd told it to globally allow the application to take control.
So now with AA and AF definitely application-controlled at a driver level, LFS' AF control doesn't seem to be doing anything for me. There's a subtle change in the foliage when switching AF between "off" and 16× (no AF seems to draw more/denser foliage) but absolutely no discernable difference in tarmac textures, white lines or barriers receding into the distance, etc.