The issue is reported by several sites :
in a video comparison ..
and now : Guru3d
The issue is not confined only to trackmania , but to a wide range of games , including Half Life 2 , The Witcher , Drakensang , GTA IV
and Guild Wars
It also includes shimmering , banding and most importantly flickering of textures .
Think about it : if AMD HD 5000 filtering was flawless , why would the company modify filtering in the new HD 6000 series ? if something isn't broken don't fix it , However filtering in HD 6000 was indeed fixed , but the fix isn't applied until you move to High Quality filtering settings .
PS : I posted this on a guru3d thread