Commuters have said they plan to celebrate the end of Arriva Trains Wales' rail franchise on Saturday.
Many are glad to see its demise after 15 years, with regular complaints of overcrowding and late-running services.
But experts defended Arriva over the fact its government contract had not required it to upgrade the fleet or factor in an increase in passengers.
KeolisAmey will take over the £5bn franchise on Sunday under the name Transport For Wales.
Glenn Page, 27, from Cardiff, has planned to hold a party in the city centre on Saturday night with hundreds claiming they will attend.
"I made it as a joke but didn't expect it to take off," he said. "As with social media, I don't know how many will turn up.
"This is nothing to do with blaming anybody. This is about celebrating the end of what has been a universally poor experience."
Official figures show complaints by Arriva customers have increased almost 30% in the last year, and in 2014 the firm became embroiled in a row with First Minister Carwyn Jones on Twitter.
But Arriva said the number of services rose by 24% and 91% of all services arrived within five minutes of the scheduled time over the 15 years.
Tony Miles, from Modern Railways magazine, said Arriva was left hamstrung for some of the problems.
"The contract for Arriva Trains Wales was let by the Westminster Labour government in 2003," he said.
"When it was let at that point, it was assumed - as it was across the rest of the UK - that there wouldn't be much growth on the railways.
"People need to bear in mind when complaining about not enough seats that if you want to get more trains you have to get permission from the government to order them and permission to then use them.
"It's not Arriva's fault. They are only allowed to do what they're allowed to do."
He said the new franchise would be different as control solely rests with the Welsh Government.
Stuart Cole, professor of transport at the University of South Wales, said he was surprised Arriva managed to keep the network running with some trains that were 40 years old.
"Arriva was required to run the railway as it was," he said.
"They took over a franchise that wasn't fit for purpose. It was an old and tired railway they ran to their credit."
He added: "The reason why £5bn is going to be spent over the next 15 years is because it wasn't spent over the last 15 years.
"It's a catch-up on what we should've had a long time ago."
Arriva Trains Wales managing director Tom Joyner said more than £100m had been invested over the last 15 years.
He added: "We can rightly feel proud to be handing over the franchise in a far better condition that the one we inherited in 2003."