I have seen one, but do not own a revolver with it on.
The company slams the S&W lock, and says theirs is superior, but they really have different goals. The S&W lock is intended to prevent use by unauthorized persons and must be operated with a special key. The Murabito safety I saw was like the safety of an auto pistol, it was simply moved down to unlock, so it does not do much to prevent unauthorized use.
The company says, "It was developed for those of us who would like to carry a revolver, but don't like the idea of a revolver without a safety lever."
Since I see no point in any safety on a double action revolver, I obviously would not spend $150 to have one installed. Incidentally, the Murabito safety does NOT allow a revolver to be carried "cocked and locked". It only prevents the trigger from being pulled when the hammer is down and the trigger at rest.
Edited to add. The Murabito safety would probably keep the revolver from being used if the gun is grabbed in close fighting, since it is very unlikely that the bad guy would know about the safety and take it off. So I will concede that point in its favor.