But that doesn't guarantee success for the country's newest social program.
The next enrollment season, which starts Nov. 15, will bring big challenges.
First off, keeping premiums and other consumer costs in check.
Close behind â?? overhauling an enrollment process that was advertised as customer-friendly but turned out to be an ordeal.
Health insurance expert Larry Levitt of the nonpartisan Kaiser Family Foundation says the Obama administration has demonstrated that the law can work, but people are a ways off from being able to judge its success.
Republican opponents of the law keep pushing for a repeal, but as millions get insurance, how long can the party's strategy remain a politically viable option?