Wouldn't own a semi without one, other than the duty Glock and 5946 I was once issued. Don't see the downside. The thinking of "my safety is between my ears" is a joke. people make mistakes. Professional shooter do. A safety doesn't totally prevent that, but it makes it less of a possibility. And since routine gun handling ND's are FAR more likely to happen than a self defense shooting, i prefer them.
And with very little time (like 5 minutes a night), drawing and flicking off safe are as automatic as pressing the brake before shifting into gear.
I carry a Ruger LC9-s with a safety. Home gun is a Ruger Sr-9. Both with safety and mag disconnect. Love them both. I wish the M&P came in a CA compliant model with the safety, mag disconnect, and LCI. Might have gotten those. But I gotta admit I am super laser accurate with the SR-9. Soda can at 15 yards doesn't stand a chance. And the LC9-S is smaller than the Shield (that I once owned).