Rather's first anniversary

This week is the first anniversary of the ''CBS Evening News With Dan Rather'' rather than Walter Cronkite. Despite the general perception that things have not gone well and the press concentration on Dan's sweater, his hairdo, and the size of his head on screen, the fact is that for the past four months CBS Evening News has been solidly in first place among the nation's viewers.

The continuing combination of Rather with Bill Moyers as commentator will be enhanced soon by Charles Kuralt's return with regular ''On the Road'' segments and even Uncle Walter on special assignments. It promises to be stiff competition for the revised NBC news with Mudd and Brokaw.

Many news executives believe that the Mudd-Brokaw combination is likely to win audiences from ABC rather than CBS, which would leave ABC even farther behind in third place than it is now. That is, unless Arledge pulls another electronic rabbit out of his back of news tricks.