The Atlanta Constitution stole the big, bold, weather map. The Austin American-Stateman suddenly turned its front page into a rainbow of color. And The Washington Post added more sports coverage.

The professional critics have dubbed it McPaper, fast-food journalism for an information-hungry America, but if imitation is the sincerest form of flattery, then USA Today, the newly published national newspaper from the Gannett Co., is making the journalistic world take notice.

"In the newspaper business, USA Today is like Rodney Dangerfield," said Heath Meriwether, managing editor of the Miami Herald. "But they do some things well."

Launched last September from an office building in Rosslyn, Va., USA Today is, if not a critical success, at least "comfortably" ahead of circulation projections, according to Gannett Chairman and President Allen H. Neuharth.

Audited figures for the last week in January put USA Today's circulation at 531,000. Gannett officials have announced that the guaranteed circulation base for advertisers will be 800,000 in April. Gannett hopes that USA Today will be selling 4.35 million copies a day by 1987, which is two years after it hopes the paper will begin to turn a profit.

Since its unveiling in the Washington-Baltimore area in September, USA Today has spread via satellite, technology to cities across the country, including Pittsburgh, Miami, Houston, Denver, Los Angeles, San Diego, San Franciso, Seattle, Portland, Minneapolis-St. Paul, Detroit and Chicago.

"They've pretty much done everything right," said Bruce E. Thorp, a newspaper analyst with the firm of John Morton & Co.

When the paper moved into Denver, it ran a front page color photo of balloonists over the Rockies. When it hit south Florida, its Life section included recipes suitable for Florida shellfish.

Gannett will add Philadelphia on March 23 and New York on April 11. Company executives will then decide where else to distribute the paper, beginning next fall. High on the list are Boston and Dallas.

USA Today is designed for the television age, from its brevity and colorful graphics down to its distinctive TV set vending boxes, and its four-section format -- news, sports, money, life -- has earned favorable notices from buyers, who say it is an "easy" and "enjoyable" paper to read.

Distinctive features include a full page of weather, two pages of news briefs from the 50 states, a crips television guide that includes some cable listings and its enormous sports section, which includes everything from late scores to high school rankings from all 50 states.

"There's an enormous appetite for national coverage, plus having local roots coverage," said pollster Louis Harris, whose firm did much of the survey research that helped shape USA Today.

Some changes have been made during the paper's shakedown period. USA Today added that staple of daily journalism, a crossword puzzle, when surveys showed that readers wanted one. Its so-called cover stories are now a bit longer (500 to 800 words) and closer to the news. And it is trying to improve its coverage of Washington.

"We have worked hard in the last few months on news out of nation's capital," Neuharth said."sometimes we've had a better feel of news around the country."

Reporters complain there is no room for nuance and that the editors -- including Neuharth when he is in Washington -- who put the paper together each day have a sometimes peculiar view of how the news should be written and displayed.

The paper does best in affluent cities, and there were complaints in Miami that Gannett was not trying to see the paper in black neighborhoods, but company officials blamed that on a lack of vending boxes.

There are also reports the paper is arriving too late in some areas to catch morning commuters. (Gannett officials say 43 percent of the papers are purchased after noon.)

Other newspaper editors say they are not impressed with USA Today as a journalistic enterprise. One editor, decrying its "utter sameness" every day, dubbed it "cookie-cutter journalism."

Tim Kelly, managing editor of the Denver Post, said the choice of front-page stories showed "they just don't seem very serious."

"It's kind of a dressed-up data bank," said Lionel Linder, executive editor of the Detroit News.

Gannett officials say such criticism doesn't bother them. "Our market is the people of America," said Walter Wurfel, Gannett's vice president of corporate communications.

Still, many editors are using USA Today's existence to lobby for changes inside their own papers, and some analysts believe USA Today may show the way to the newspaper of the future.

Said the Detroit News' Linder: "It will force editors to reexamine the way they've been editing papers. They may say, "Gee, we've been making it tough on our readers.""

The Detroit Free Press gave USA Today free to 78 people to determine what readers thought of it. Executive Editor David Lawrence said people liked the late sports scores, the informational graphics and the weather map. The Free Press has changed its weather report and television listings after studying USA Today. But Lawrence said its test readers complained about the lack of local news and advertising in USA Today.

Local publishers and editors say USA Today has not cut into their circulation, and Neuharth maintains that his baby is not designed to compete with local papers. "We're an additional buy," he said.

Instead, USA Today hopes to attract mobile, affluent Americans with a yearning for news from back home and a strong appetite for information.

"No way it will compete with local papers," said Lou Harris. "Ultimately it should take away from the newsweeklies." Already, he said, close to a majority of USA Today's readers also read newsweeklies, and the paper was designed with such publications as Time, Newsweek, Sports Illustrated, People and Business Week in mind.

Gannett spent an estimated $20 million getting USA Today started, according to industry figures, and it losses this year may total $50 million. Still, the new venture hardly appears to be a threat to Gannett's survival. Gannett reported last month that its 1982 earnings set a record for the 15th straight year and 61st consecutive quarter.

The key to the paper's ultimate success will be advertisers, however, and no one is certain how well it is doing there, in part because Gannett offered early advertisers six months of free space if they signed a 15-month contract. Neuharth said that advertising volume is about 50 percent ahead of projections, but "on revenue, we didn't project very much."

"We gave it a 50-50 chance from the beginning," said newspaper analyst Thorp. "We're still not ready to change that, although things are beginning to look a little more favorable. The readers are coming through."