For the most part, the extra channels (the ones we get without cable or digital TV like your local news channels) will be used for public safety news. Really, a major reason for the DTV switch is to free up frequencies for public safety communications (police, fire, and emergency rescue). 

Digital transmission is significantly more efficient technology that allows broadcast stations to offer improved picture and sound quality, (who doesn't love their bass!) as well as offer more channels- which in turn will offer more programming options for consumers through multiple broadcast streams (multicasting).