"It gets better every day," boasted Mayor Marion Barry as he sat down with a plate of spiced shrimp, pate and scallops at a party commemorating his administration's first 100 days.

Across the crowed room at the Club LeSerre in Georgetown, Effi Barry just shook her head saying, "I can't believe 100 days have passed. I'm just happen to be part of something so positive."

Around the light, airy space of the club, packed with Barry campaign contributors and workers, the assessments were predictably positive.

Stuart Long, a restaurateur and the largest fund-raiser for the Barry campaign, said his investment was bearing fruit. "I like his jobs program and once he got in, I knew he'd find out the headaches of the businessman. He's starting to work on issues like workmen's compensation, said Long. "And I know the restaurant association has written him five letters and gotten five replies all within a week. That never happened before."

Robert Washington, chairman of the D.C. Democratic State Committee, who was once determined to see Sterling Tucker become mayor, added his own praises. "He's been exciting, innovative and decision," said Washington, citing Barry's quick call for an investigation of the recent mental-care foster home fire.

Though the euphoria of the victory of the Barry underdog campaign hasn't worn off yet, most of the guests said 100 days was too soon for firm judgments. Ed Lewis, a business consultant who worked in the first 17 months of the Carter administration, said "A hundred days is just a start, but Barry has certainly made strides by making his views known." One of the many people who has moved inside the District Building since the campaign, Mary Lampson, commented, "We haven't stopped working, but no matter how hard you work, you still feel excited just from moving forward." CAPTION: Picture, Effi and Marion Barry; by Harry Naltchayan-The Washington Post