My revolver was in Springfield for warranty service, on S&W's dime, so I had them perform the Master Action Job while they had it.
I had backed-off the strain screw when I got the gun, which lightened the DA pull a little, but the gun was only 80-90% reliable with my handloads if I didn't use Federal primers.
When the gun returned from service, I was a bit disappointed to find the only difference, other than the chamber mouth chamfering, was the strain screw was tight.
Pull weight was the same, ignition reliability was the same, and not much in the way of noticeable smoothness.
If someone had told me that the $125 spent was going to have about the same functional effect as a quarter-turn of the strain screw, I'd have opted to save the money.