I've seen them too, though the ones I've seen were just being used by detectives or something and definitely not setup for patrol.
Around here their still in the test phase, the state isn't going to just drop everything and switch to these new cars. They have to use up all the light bars and parts they already have in stock for the Crown vic and consider the costs of essentially "retooling" for the Charger's. Plus consider reliabilty, fuel, and a few other factors.
I like the charger over the crown vic but that's just my opinion and I really don't care what car they choose as long as they don't waste our tax dollars taking one over the other.