Time, and plenty of it, will be the true test of the most significant reform of U.S. health care since the 1960s, these pundits agreed.

Caroline Pearson, a policy analyst at Avalere Health, said she'd be basically ignoring all the palavering from the right and the left in the early weeks of the exchanges' lives. No one fact or figure, no single analysis or survey, will yield a definitive answer, Pearson said.

"There's not really a good way to answer the question," she told the National Journal. "There's no apples-to-apples comparison. Is one product being sold today to one group of people going to be more or less expensive than a totally different product sold later to a totally different group of people? There's no way to compare those two in a way that would be deemed fair."

Only slow and steady returns over time will begin to offer clues as to whether the PPACA will truly extend affordable health care to the masses, and even then, neither side will admit defeat, said Devon Herrick, senior fellow at the National Center for Policy Analysis.

"I don't think the proponents will ever admit it's a failure," if it turns out to be, said Herrick.

The success or failure of the state insurance exchanges will be largely dictated by how many people — and specifically, how many millennials — sign up for coverage, Herrick said.

But nothing will dissuade "the doomsayers and cheerleaders" from jumping to instant and greatly exaggerated conclusions, Pearson predicted. 

"I think the challenge is that people want to have something to weigh in on," Pearson said, "and nothing has started yet."