After being prior military and tons of armed security training and the like. By the time you pull your weapon (Edit, be PREPARED TO SHOOT) it is time to shoot. If you pull your weapon to threaten someone, then your wrong. open carry is better for deterrence.
Edit: every situation is different, ive always been in the mind set of open carry and visual deterent. for me it comes down to very last resort on drawing a weapon. I also pack pepper spray for the less than lethal approach.
if something were to happen just try and keep as much distance between you and the aggresor. If someone comes at you with a knife, the law as I understand it is 30 feet. 30 feet normal people can come very fast and close the distance to stab you. so situations like that, then blammo, knife to a gunfight thing. Unless your out going shooting there is absolutly no reason to draw your weapon Edit: IN A AGGRESIVE MANNER. EVER!
As far as shooting someone, absolutly, I do enjoy my life and want to continue living. so in self defense, with out a doubt.