It seems the issues are 'inadequate driver support from AMD and Nvidia'... http://uk.pc.gamespy.com/pc/id-tech-5-project/1199038p1.html ... here is Bethesda's official blog with the latest drivers and suggestions: http://www.bethblog.com/index.php/2011/10/07/playing-rage-on-pc/
Not really any mods since they haven't released the SDK yet which was supposed to ship with the game. They did add a detail option to the GFX menu to try and improve the textures, but just makes them look noisy and worse off imo. You can try the graphics tweak shown here:…