Once you decock a Sig, the trigger pull switches from single-action (~4# pull) to double-action (~10 pounds). If you have a problem with "accidentally" discharging handguns with 10lb. triggers, you have a serious TRAINING problem.
This is the same philosophy that has worked for decades with double-action revolvers, so again, if you're not OK with the idea, it is a software problem, not hardware.
So the answer to your question is "YES". It does add a great deal of safety to the handgun. Plaxico's problem was that he wasn't using a holster of any kind, let alone a GOOD ONE; a universally stupid idea.