Every little bit helps. The shutter can jar the camera. It's generally not noticeable except at slow shutter speeds (long exposures). It can never hurt, but can often help. For serious landscape and macro shots I always use it. The idea is to let the vibration from the mirror up slap die out before the image is captured, eliminating camera shake. If you're shooting at 1/4000 you don't need to worry. But at slower shutter speeds it can become an issue.