Driver shaft fitting does make a difference. Even if you have been fit before, things change and getting fit with the option of testing multiple head and shaft combinations will make a huge difference.
The example in the picture on the left is of a college player that we fit roughly 18 months ago. His swing speed averaged 101 mph with a medium tempo and mid release. We dialed him into a Kuro Kage TiNi 70 at a 6.6 flex (low X Flex) in an R15 430 set at 8.5 degrees. His shot dispersion was very tight while his miss was a little draw. This summer his misses started being a little more left and his ball flight was a little too high so he came back in for a re-fit. His swing dynamics had not changed (tempo, release, attack angle) but he had definitely gotten stronger as his club head speed went up to 105 mph. After testing three different shafts, the winner in the bunch was the Project X HZRDUS Yellow 75 built to a 7.2 (high X stiff) in his new TaylorMade M1. The back weighting of the HZRDUS Yellow helped us keep the swing weight at a reasonable D5 at 45 inches. The M1 is a heavier head so these back weighted shafts really help. The Kuro Kage TiNi 70 was a close second at a stiffer flex, but our player liked the feel of the HZRDUS 75 better.
The result was a huge decrease in shot dispersion and misses that were actually slightly right of target. For any golfer we fit, the goal is to tighten shot dispersion and make your misses more controllable. And, if you get more distance, that is a bonus. Mission accomplished. So if you are struggling with accuracy, consistency and distance, get yourself to a qualified clubfitter that has multiple shaft options for you to test either with your head or a head that has better performance. You should see some great improvement!