There are similarities between the two programs, from the political fight over their enactment to the difficulties in making the laws a reality. But the laws differ in some important ways, too, including ones that supporters haven't fully acknowledged.
So what can we take away from Part D? Here's a quick guide to lessons from the drug plan's rollout.
How they're similar: Both launches were filled with glitches. The Medicare Prescription Drug Plan finder's launch in November 2005 was about a month behind schedule. That website also was slow, missing key information, and took time to fix, notes Georgetown health scholar Jack Hoadley, who has blogged about lessons from Part D's implementation.
"The level of frustration for those using the site was pretty high in 2005, just like today," Hoadley told California Healthline earlier this month.
How they differ: In many respects, Medicare.gov was less important to Part D than healthcare.gov is to the ACA.
The new insurance exchange websites are seen as a key linchpin of the law; they're intended to allow millions of Americans to browse different coverage options, see their subsidies and check if their preferred providers are included.
That personalized shopping experience is one reason why the online features are so crucial and call centers aren't a perfect substitute. As the Huffington Post's Jeffrey Young recently reported, the ACA wasn't really designed for shopping over the phone.
And it's also a major departure from 2005, when most seniors didn't turn to the Part D website on their own. Surveys suggested that nine out of 10 seniors went through brokers, family members or other helpers to select their new prescription drug plans, according to one report.
The Urgency of the Problem
How it's similar: Both high-profile laws came under widespread scrutiny, with front-page stories and network news reports devoted to their rocky launch.
How it differs: While criticism of Part D did focus on the law's unexpectedly high cost and troubled launch, there was also a public health component: Seniors were increasingly nervous that they wouldn't get their drugs.
Current challenges with the ACA, meanwhile, center on the political and policy implications. Many of the nation's poorest and sickest patients already are being helped by provisions in the law that expand Medicaid and bar insurers from excluding customers based on pre-existing conditions.
The Political Environment
How it's similar: Just as Democrats fiercely resisted Republicans' efforts to enact a Medicare drug benefit, the GOP refused to support the Democrat-led ACA.
How it differs: While Part D is seen as successful today -- 90% of seniors were satisfied, according to a 2009 survey -- Democrats say that their party deserves some credit.
"We lost the policy fight, and what did we do?" asked Rep. Bill Pascrell (D-N.J.), at a hearing on Capitol Hill on Tuesday. "We went back to our districts and we told our seniors although we voted no, we … will work with the Bush administration to make it work," Pascrell added.
"And how many of you stood up to do that" for the ACA, Pascrell asked his GOP colleagues. "None. Zero. Zero."
How the White House Is Managing the Situation
How it's similar: Both administrations were forced to scramble to address the dual problem of fixing the program while managing public perception.
How it differs: The Bush administration quickly implemented a policy of "almost over-sharing information," one former official told California Healthline; for example, CMS officials held regular meetings with industry stakeholders throughout the fall and winter of 2005, with daily updates on the state of the Part D rollout.
But the current White House adopted a "bunker mentality" for weeks, David Nather writes at Politico, offering few details over what went wrong and how soon it can be fixed. While officials are now shifting gears and offering more transparency, NBC's Chuck Todd on MSNBC's "Morning Joe" on Wednesday morning said that the White House remains hunkered down. The Obama administration is nervous, Todd said, that "their entire second term is going to be judged on the implementation of health care."
What We Still Don't Know
By the end of November 2005, about two months after its original scheduled launch, medicare.gov was "well-designed and easy to use," one New York Times reporter concluded.
Will healthcare.gov follow a similar timetable? Obama administration officials have pledged that the exchange websites will be mostly working by late November, which would still allow for a four-month open enrollment period.
That gets to another interesting comparison: how will sign-ups through the ACA compare to Part D?
Obama administration officials acknowledge that early enrollment numbers will be low -- HHS Secretary Kathleen Sebelius on Wednesday morning told a House committee that the figures will be "very small," largely because of problems with the exchange website.
But Georgetown's Hoadley notes that the decision to purchase health coverage is a complicated process, pointing to the slow uptake for Part D: about 8 million seniors waited to sign up until after Jan. 1, 2006.