Nasty. ***NSFW Language***
I have to disagree with the self inflicted victim -- negligent discharges do not happen. It is not something a gun owner should expect or believe will happen to them at any point in time. You do not practice gun safety with the expectation that it will happen to you; you practice gun safety with the expectation that you will not be the one on a YouTube video expaining how you shot yourself. Also, the blame does not lie with the safety being inadvertantly disengaged when you draw from the holster because your finger should not have been inside the trigger guard until the sights were on target.
That being said, I don't like holsters with doodads on them. This includes the Blackhawk! Serpa holsters, of which I have several and use them. I see the Serpa as being a safer alternative in a retention holster when you re-holster, as there are no flaps to worry about finding their way into the trigger guard like with a snap holster.
Finger is only authorized to be on the trigger when you are ready to shoot.
Rule #3 - "Keep your finger straight and off the trigger until you are ready to fire."