GRiD is a great game. It's NOT the best racing game ever created (by a long shot), it doesn't have the most cars, and it doesn't allow you to customize your cars (other than colors and sponsors), but it does have a great amount of variety and action. The physics aren't the best, but they're far more realistic than your average arcade racer (Need for Speed series, for example). I also find the AI to be pleasantly adequate, only lacking in aggressiveness in turns and crash recovery.
It works fine with the keyboard for me (WASD for accel / brakes / turns, up and down keys for shifting), but I had to tweak a few settings in the options menu to get the turning "radius" correct and other twitchy-ness.
For ~$6, everyone should grab it.