I know the striker down/no safety/round in chamber is popular with some African PH's, but I personally don't like it. The firing pin is resting against the primer, and a jar or bump could cause a discharge, and this is not just theory.
I almost always carry round in chamber/safety on. One exception is my Marlin .22 mag... safety is backwards to what I'm used to (forward is safe, back to fire... wrong, wrong, wrong!). In that case I carry chamber empty and only load up when I'm offered a shot. The primary safety is the one between your ears; the one on the gun is secondary.