Minus a few bugs, it's perfect.
There's not much to say negatively about this game. It has a very nice and simple design, it's addictive, challenging, and has some decent music. If this were to be released as say an iPhone app, or perhaps and Xbox Live Indie title, I wouldn't mind putting a few dollars for it.
One annoying glitch was that if you were to jump diagonally and enter a car, you still get the points, but the game thinks you're still in your original car. It can be confusing if you're trying to rack up a combo. Also I think maybe the car that the player is controlling should glow or something just so it's more clear as to which car you are using.
Other than that though, it's amazing.