I actually bought this game for my iPod touch since it had great reviews, but was frustrated by the control issues you see here (and was thus skeptical of the gaming potential for the iPad).
There simply is not enough "buttons" to control moving, aiming, and looking at the same time. Yes, the accelerometer or another button might help, but ultimately I think that the problem is that pc/platform gaming simply does not translate perfectly to touch screen gaming.
Another problem I have with the driving games is that they want you to use the accelerometer to steer. Hell, I have to LOOK at the screen to see where I'm going, so tilting it and turning it this way and that does NOT improve my ability to drive.
Still, other games that involve physics, or turn based games like Civ Revolutions work great. I think it's about finding the right game/interface for the platform.