Scrap Metal is the first arcade twitch racer that feels at home on iOS. You touch a part of the screen and you drive there -- this has to be experienced to be understood.
Also, its more than a racing game. I had the most fun in the demo derby smashing cars up. Be sure to try that out too.
Runs great on my iPad even with the advanced effects including rain.
Frogtoss about Scrap Metal, v1.0