Nothing strikes terror into the hearts of planners of local holiday shows like the news that the Rockettes are coming to town. The touring version of the Radio City Music Hall Christmas Spectacular has been a mass-marketing juggernaut in many cities, severely cutting into ticket sales for local productions of The Nutcracker and other holiday favorites. But in Denver, where the Radio City show is debuting this year, “the show’s ubiquitous advertising and numerous public appearances have brought earlier and increased awareness to all consumers of their impending holiday entertainment choices. And early returns indicate everyone seems to have benefited.”