The biggest advantage that I find with the match trigger setup on the USP is the trigger break. The standard hammer, when cocked, has a very slight bit of travel just before it breaks to strike the firing pin. With the match hammer, there is none...just a nice, crisp release. If you have a stock USP, you will be able to see what I mean...#### the hammer, and slowly apply pressure to the trigger without actually making the hammer fall...kind of like a light, pulsating pressure on the trigger...you will be able to see the very slight movement of the hammer just before it breaks. That is what is eliminated with the match hammer, which for me, makes a HUGE difference.
I'm not really a big fan of very light trigger pulls, so I retained the factory hammer spring and trigger return spring. I do like a smooth pull, so I did install the nickel plated sear spring...helped out a bit, but not as much as I thought it would.
The over-travel adjustment on the trigger, or trigger stop as it may be known, does add that extra bit of "crisp". It works really well to eliminate that bit of sponginess after firing, and just gives the the trigger a much tighter, more positive feel.
Just my 2 cents...