Now that I have had some training, my comfort zone is about 50'.
Just kidding, sort of. I realize more just how long it takes to actually deploy my weapon. I have read enough to know that handguns are lousy excuses for one-shot wonders. Just because I hit 'em doesn't mean they're quittin'.
In reality, if I have a bad feeling about someone, I don't want them closer than 10'. But that's almost impossible in many environments.
Unless I am going to move to Idaho or Montana (more sheep-baa baa kind-than people), I'm not generally going to be comfortable most of the time.