When I was in the Air Force anytime we were flying we were issued M9s (Beretta 92FS). As far as I remember, the 92 series has the standard internal safeties that all modern guns do for drop protection, decocking, firing pin block, etc. Depending on uniform required, we were issued the M9 (green nylon) holster or the shoulder holster. Standard operating procedure was to load the magazine into the weapon, rack the first round into the bore, decock, switch the safety off, and holster. We trained this way exclusively and (for Air Force) extensively.
Problem was, those holsters tended to rub the safety area and about half the time, when you drew, the safety was magically back 'on'. Nothing for pucker factor than a gun that doesn't work, with no backup arm, someplace unhappy in the world. When stuff hits the fan you can only be as good as your training, and we weren't trained for accidental safety engagement. We weren't cops that draw on folks to enforce compliance. If an AF flight crew member draws on someone shiiat is getting way too real way too fast. It is an experience you will have indelibly etched upon your brain and will revisit every time you look at or handle a gun from then on.
I still stand by my statement and belief that external safeties on a defensive handgun are there to kill the owner. See the retarded keylock safeties on newer revolvers, that were basically demanded by the Feinstein's Monster in California. As a lawyer, I understand the putative liability aspect from the manufacturers' viewpoint. I also note that I cannot find a single instance of someone successfully suing a gun manufacturer for a death or injury to the *owner* that resulted from the gun not operating as expected in a defensive situation.
The natural response to this diatribe is this: "Well then, don't buy a pistol with a safety. There are plenty out there." While this is true, none of them are as good a carry weapon, IMHO, as a Shield with this one issue. I think perhaps some engineer at S&W realized this fact as well because in most handgun lockwork I've seen, just removing the safety makes the whole shebang not go... bang. I wish they made a 48-state version like they used to do with vehicle emissions. But they do not. So we're left with removing or disabling the external safety, to ensure it performs as expected 100% of the time.
Again, if you've spent your life training with 1911s, then ignore all the above.