Firstly, are any of us a good enough shot to neutralize the threat without the possibility of 'collateral damage?' Secondly, add the adrenaline of a high-stress situation to that and your answer SHOULD be a resounding "no." I've been military/law enforcement for 10 years now with extensive gun and defense training and I can safely say no. Thirdly, we as LEOs are ALWAYS taught to "not be a hero." Why is that? Well, what's the difference between a CHL holder and a hero? The CHL holder is still alive.
Now, if all the variables that have been discussed so far are in the CHL's favor you're damn right I'm going to take the shot. Also, it has been proven time and again that MOST (emphasis on MOST) BGs will turn tail and run when confronted with the pointy end of someone else's gun. So perhaps just the show of force would be enough to neutralize the situation completely...perhaps not. There's a lot of tactical thinking that needs to go with this scenario. (most of which have already been mentioned i.e. other BGs who have not revealed themselves yet, other CHLs who may be thinking the same thing you are, etc...)
This question should refresh everyone's mind that one should be always testing himself while carrying. Constantly be aware of your surroundings and play 'what-if' scenarios in your mind...even while sitting at Chili's enjoying dinner with your XYL.