EVERY time I play I lose my save files. At one point I had every item, the brick, omega, and every bonus shop item. now I can't even get to the omega stuff because it takes too long, and it doesn't save.
I'd give a 9/10. The timer is set to give the player a real scenario where you have to get out of the city in time. It would be nice to have a free play once you beat the game on challenge mode though. Good game!