Paul Kedrosky, of Infectious Greed, and well-known writer for Wired and many other sources, including the WSJ, says that Tiger hits the ball too hard, trading off distance for accuracy. Paul has a really nifty flash chart showing that over time, Tiger's distance has increased by a small amount while his driving accuracy is slipping considerably.
As you can see, despite the supposed improvement in his game, Tiger's driving accuracy has fallen off much more than his driving distance has increased. At the same time, the gap between Woods and the mass of his professional competitors is much smaller than it was five years ago -- the animation shows this nicely, with a great splotch of competitors all closing in on Woods over the period.
Go see the flash chart. It shows the trade-off results nicely; it's worth a look.
What are the shadow prices and elasticities of accuracy vs. distance on the PGA tour?