The new stations are located at 72nd, 86th and 96th streets, and provide an extension of the Q line that will now connect the Upper East Side in Manhattan directly with Brooklyn and Coney Island. There are three more phases planned for the project.

But in addition to the improved transit connections - now, Upper East Side residents can reach Times Square without swapping trains - the debut of the new stations has been hailed for the unconventional design of the stations. They’re spacious, airy, with high ceilings, an expansive mezzanine level, and ambitious public art installations.

“I hope when you go down there, you’re really going to feel it’s worth it,” said New York Governor Andrew Cuomo outside the 96th Street station on Sunday, thanking the local residents and business owners who endured years of construction work. “This is a subway system like you’ve never seen before. It’s not your grandfather’s subway.”

In the crowd were upper-East-Siders Kaz Tanakh and Mark Conrad, self-described transit die-hards who wore New Year’s Eve party hats directed with yellow “Q” stickers to celebrate the opening of the stations. They took selfies outside of the station’s sleek glass entrance.

“A month ago, we thought there was no way this could open on-time,” Conrad said. “The streets were just a mess, and traffic was horrendous - it was like L.A.”

There was Lawrence Scheyer, a 61-year-old living in Stuyvesant Town, whose grandfather was a chief designing engineer for the New York subway system and had always hoped to see a subway running along Second Avenue.

“It’s an homage to my grandfather’s legacy,” Scheyer said, though he added that he remained disappointed that only three stations were opening, rather than the rest of the planned extension toward East Harlem, which has not yet begun construction. “It should have been built in one fell swoop.”

At exactly 12 pm, the crowds followed Cuomo down the escalator and into the station’s mezzanine level with clapping, cheering and calls of “Yeehaw!” They shot cellphone videos of the mural on the walls and gaped at the high ceilings. Then they packed onto the trains and headed downtown. The speaker system crackled alive. It was Cuomo, speaking into the intercom from one of the rail cars.

“Rest assured, I’m not driving the train!” Cuomo said over the train intercom as it barrelled through the tunnel. He praised the project’s managers for completing the first stage of the subway extension on-time and on-budget “You’re on the inaugural ride. It is exciting - a great way to start a new year in New York.”

At 72nd Street, many of those riders disembarked to soak in the design station, where there were already crowds of people seeking an opportunity to get one of the first looks of what was inside. One of those people was 33-year-old Lindsay McLoughlin, who lives a short distance away on the Upper East Side.

“It’s like Disneyland for the commuter!” she gushed to her mother as she stepped off the escalator and onto the platform, grinning and turning in a slow circle.

“I’ve lived here for eight years in a fifth-floor walkup, which is a challenge in itself,” McCoughlin elaborated. “Just to have to walk three fewer blocks to get on the subway - it’s like meeting Mickey Mouse for the first time.”

Siblings Michael and Ellie Mellor, 9 and 7, were equally enraptured.

“It’s really cool to be on a new subway!” Ellie said.

“And being one of the first kids to get in!” Michael jumped in.

Their father, Jim Mellor, had his own reason to be thrilled about the opening.

“I’m hoping it will alleviate some of the intense crowding on the 6 line,” he said.

Not everything was perfect for the subway debut, however. One of the first trains scheduled to leave the 72nd Street Station, already filled with riders, held at the station for about 20 minutes as Metropolitan Transportation Authority officials announced that the delay was due to train traffic up ahead.

Thomas F. Prendergast, president of New York City Transit, acknowledged that the wow factor of the new stations’ visual design won’t mean much if it’s not coupled with punctuality and reliability.

“We’ve gotta follow through with good, on-time service,” Prendergast said. “And we will.”

Up on the mezzanine level of the 72nd Street station, crowds gathered along the walls to get a closer at the artwork - a series of dozens of mosaics by the artist Vik Muniz, each of them a portrait of an average New York subway rider. There were kids in soccer gear and a woman in a sari staring at her cellphone. A man holding a bouquet of balloons, and a woman carrying a toddler in one arm and a stroller in the other. A white-collar worker depicted in a clutzy moment of tripping, his briefcase tumbling out of his hands as stacks of papers burst out. Two men, in flannel and jeans and overalls, holding hands. A police officer holding a Popsicle.

Riders snapped shots of the mosaics. Some posed next to the artwork. But many just wanted to take a close look, their faces inches away from the wall, their fingers brushing against the tiny glittering tiles.

“What I love was seeing how people responded to it. It’s really quite wonderful,” said Jock McLellan, 76, from Connecticut.

“The art is spectacular - the inclusion, the young and old, black and white, immigrants, readers, travellers,” said Deborah Daughtry, of Ridgewood, New Jersey. “It gave me goose bumps.”

Daughtry came with her partner David Burnett. Neither of them commute frequently to the Upper East Side, but they treated the excursion like a visit to a museum.

“He dragged me out of bed this morning to see it,” Daughtry said.

Burnett, too, was amazed by his surroundings - but for slightly different reasons.

“I don’t know why it needs to be this big,” he said, chuckling and gesturing at the expansive space. “These would make great condos. Think about how many studios can fit inside here!”