The game is fun, up until track 6. After that, even with max upgrades, it has a feel of 'you collided with a blade of grass, we're going to have 5 cars pass you, with no chance of regaining your position.' Nos boost on track 6 is absolutely worthless, in second place and trying to pass the car in front of me I gained no ground, the car in front of me kept his distance regardless. Once you drop from first to second place you're SOL. It would be more fun if there was a slight CHANCE to pass him.
Physics seem a bit crude, but I'm not expecting Gran Turismo.
As someone said in a previous review, the screeching tires get annoying, I would suggest maybe limit it to when the car is going around the tightest corners or something.
Graphics? Graphics are fine, it's a flash game ffs. What are people expecting?