While most of the media attention today is going to the other rule change--how the slide rule will be further enforced to protect vulnerable middle infielders from getting leveled like Ruben Tejada was by Chase Utley last October, I believe shortening commercial breaks by twenty seconds each half inning is the bigger story. This will take at least a full six minutes off a full nine-inning game. It will also create a better game flow and less channel clicking by fans watching at home.
This is clearly an effort by MLB to keep younger fans interested in baseball, as many have embraced the faster paced action of sports like basketball and football (although the NFL has had their own issues in recent years with games running too long).
This is a good move by MLB. Now a good next step would be to have Saturday World Series day games and earlier start times for the post-season night games.