All my life, I've had a screen door which is always kept locked - my logic is that if a robber knocks on the door and I open it, I have the locked screen between them and me (because robbers don't climb through windows in my mind!).
However, we want to get a new front door, one of the ones with horizontal glass panels, however they look so nice that I'm not sure whether I want to cover it with a screen. So I'm looking for your advice, do you not have a screen door? How do you feel opening the door when someone knocks and you're not expecting a visitor? Or do you have a screen door that you can see the glass door through?