This post from the Codemasters forums has links to 3 graphics mods for GRID that improve the look of the game for those who can run it.

http://community.codemasters.com/t5/GRID-2-General-Discussion/Race-Driver-GRID-PC-Graphics-MODs/td-p/255104

Let me know if it works out for you who own the game. It just might convince me to go through with purchasing it.