Neat idea, like the various events. Could use a few more, also the pill price was a bit odd, and later would let me buy them for a 1$ when I was at a 1$ from the last event, need's a min/max price still if it's based on your money available.
I liked the description changing as you got bigger, but I think this only happened once. I could see the need to get a car upgrade at the end of each lap, i.e. something to save for. A HUD showing your info would be useful too.