The driving can get weird at times, just driving around in a circle keeps you somewhat invulnerable, the upgrades don't seem to count zombies I've killed.
Weapons are more important than speed, since not all zombies jump, and they come at too rapid a pace. I would like the game extended, slowed down, and have some tactics on when I fire, and when I shoot.
Maybe I'm in the minority, but I find these games hopelessly repetitive. The interface doesn't change, the tutorial is cut and pasted, with no option to skip for those who know what they are doing. But worse of all is that the gameplay is the same. Drag an order, click, wait, click again, wait, click with some accuracy, watch a customer scrutinize your work.
Walk of the screen to the right