I feel the need to clarify though...
Jeff's comment in this thread is not on target for the question asked. Playing multiple hands isn't required to get an advantage over the dealer in high counts. E-town-guy and LeonShuffle covered most of the reasons why high counts are better for the player than the dealer, but I'll recap...
You'll get more blackjacks. So will the dealer, but he wins only even money while you get 3:2.
You'll get better results on your double downs (though you'll get fewer opportunities to double!)
The dealer will bust more often, because he must hit on totals of 12 to 16. Compare that to an increased value of your ability as a player to stand on stiffs in high counts.