The Tom Cruise shooting clip in your avatar shows that it was special effects and not quickness. Think about it! When did you ever see the barrel not flip up when shooting a major caliber? Also, the muzzle flash is a bit excessive unless it was cheap slow burning ammo, which I doubt a pro hitman would use.
What is interesting is "the making of" on the DVD. The actor spent a lot of time on a range with a special instructor and live ammo in preparation for the role, practicing against paper the very moves he executes on the screen, which is why the shooting scenes are convincing.
This gun store owner mentioned to me once that firing a USP without ear protection is not very smart. He was saying they are extra loud. I wouldn't know. I do like how Tom Cruise's character doesn't seem to be fazed by that though.