The fact that those survivors in the car at the end took the decision they did seemed wrong to me. I know they'd been through a lot, and I guess their hope had run out wit the petrol. But these are the people who would fight when others were paralysed by fear. The people who didn't just give in to religious hyperbole and go with the flow. If I was them (and I'm not particularly brave but I'd accept the unknown of the mist to the finality of the bullet any day) I'd have gotten out of the car and proceeded on. Or at least stayed in the car and see what happened. If that woman in the back of the truck proved anything, you never know what will happen, although they of course weren't aware she had survived at that point.
I'll admit that after he did The Deed and waited for the monsters to do their thing.... and the tank rolled out of the mist , I roared with laughter though.