Really nice game for a first big project.

Some suggestions:
1) Make the levels harder
a) Make the car harder to control (ex: skidding)
b) Make collisions a little bit more damaging (after hitting the wall, make it harder to get back on track. It didn't really matter to me if I hit the walls or not because there really wasn't much penalty. The car deccelerates and accelerates so fast that slowing down around a turn is basically the same as hitting a wall.

2) Make it more competitve. Most people won't have another person beside them while on the computer. You could add a timer and have a highscore board. This will increase replay value, expecially since there is no opponent AI. Either that or record the player's best time using sharedObjects so one can attempt to better oneself. Or even better, record the "shadow" of run with the best time, and play that during the race, so the player can race against himself.

That's it for now. Once again, great start =)