Diane Sawyer has now officially left CBS News and, after a short vacation, will report for work at ABC News, where a fancy new office is being prepared. Back at CBS, some people still find it hard to believe she decided to leave.

Sawyer may not have set the world on fire with her journalism while at CBS, but she became a truly lustrous figure. Losing her was a serious blow to the dwindling prestige of CBS.Insiders say the reason was not money. ABC News will pay Sawyer $1.5 million a year, not that much more than the $1.3 million she got at CBS. The reason she left is that ABC News President Roone Arledge promised her a rose garden-a much better showcase for her talents than she got at CBS.

By one account, Arledge used to call up Sawyer after her pieces appeared on CBS and tell her how much better the treatment of them would have been on his network. His courtship of Sawyer was relentless and went on for months. "Roone is wonderful at putting the stone in the setting," one network veteran says.

Diane Sawyer is but the latest jewel for Arledge to polish. David Brinkley was feeling unappreciated at NBC News, so Arledge showered him with attention and offered him his own show at ABC. The result: "This Week with David Brinkley," now in its eighth year and the best of the Sunday morning interview programs.

Brinkley was completely rejuvenated and now is as happy and contented as the Keebler elves.

Arledge has made stars of Ted Koppel, Sam Donaldson, even as unlikely a TV reporter as Jeff Greenfield. With the acquisition of Sawyer, ABC now is home to the two most imposing women in broadcast news, Sawyer and Barbara Walters. Indeed, the Sawyer move may have been enough to tip the balance of power to ABC News for the first time in history. Or at least the balance of glamor.

CBS News still, of course, has Dan Rather, Charles Kuralt, Lesley Stahl, Mike Wallace, Bob Schieffer, and a host of others. It remains a house of powerhouses. But even Walter Cronkite threatened briefly to leave last year, suggesting CBS is doing a bad job of keeping its hot-shots happy.

While CBS did lure Kathleen Sullivan, one of Arledge's protegees, away from ABC, she hasn't turned out to be much of a catch. The "CBS This Morning" she co-anchors gets ratings as terrible as ever, below those Sawyer got when she coanchored the "Morning News" show with Bill Kurtis.

Sullivan has gained ten pounds. Her performance on and off the air is quixotic. She could not be called a good trade for Diane Sawyer.

Is it sexist to comment on the way woman journalists look on the air? The double standard remains. Charles Kuralt is bald and fat, but no one seems to complain. Fairly or not, there is still more pressure on female personalities than on males to be mindful of their appearance.

Clearly, Sawyer is a knockout. She's beautiful enough to have been a Hitchcock heroine: the icy blonde. Some insiders think it's her glamorous aura, more than her journalistic credentials, which has made her such a hot property. Although the "Morning News" never became a hit, it did make Sawyer a star. She jumped ship the minute she got too big for the show.

CBS News President David Burke reportedly did not try hard enough to keep Sawyer. Burke, who came over from ABC News himself last year, waited too long, sources say, to offer Sawyer her own prime-time program. The plan was to dump "West 57th" on Saturday nights and put a new Sawyer show there.

But it was too late; Arledge had already turned Sawyer's head. Now CBS is reportedly making the same offer to Connie Chung of NBC News.

On ABC, Sawyer will co-anchor a new prime-time magazine show with Sam Donaldson. The program, still without a title, will most likely air in the Thursday night timeslot opposite NBC's "L.A. Law," the home of ABC's "2020" until it moved to Friday. Arledge refused to cast the program until he had won Sawyer's heart.

Some churls at CBS say that one reason Sawyer left is because Rather considered her a threat, a rival he was glad to see vamoose. But a source close to Rather says the story is ridiculous and that Sawyer and Rather had a good working relationship.

Nevertheless, Sawyer might eventually end up coanchoring "World News Tonight" with Peter Jennings at ABC, something Rather would probably never have permitted at CBS. For Sawyer, the possibilities at ABC are almost limitless. At CBS, she was just another superstar.