Let me offer a ludicrously premature opinion: Barack Obama has sealed his reputation as a president of great historical import. We don't know what will follow in his presidency, and it's quite possible that some future event--a war, a scandal--will define his presidency. But we do know that he has put his imprint on the structure of American government in a way that no Democratic president since Lyndon Johnson has.
The last two generations have no model for such a president. The only two other Democratic presidents of the last four decades are Jimmy Carter, a failure, and Bill Clinton, who enjoyed modest successes but failed in his most significant legislative fight. Obama, who helped pull the country out of a depression and reshaped the health care system, has already accomplished far more than Clinton. (This isn't necessarily Clinton's fault--he lacked the votes to break a Republican filibuster that Obama has--but the historical convention is to judge a president by what he and the Congress achieve together.) He will never be plausibly compared with Jimmy Carter.
First of all, ouch. The Carter presidency kicked in the nuts again.
But anyway.
Even without healthcare reform, President Obama would have been viewed as an historically significant chief executive -- the first African American president, and, you know, the whole rescued the world from the brink of another depression thing. But healthcare reform adds a layer of success that extends beyond the reach of those items.
It's a policy victory that stands alone with a sense of the longview. In other words, the election was a political and cultural victory, but not a policy victory. The recovery bill was a policy victory, but a reactive one. Healthcare reform not only has been a century-long endeavor finally achieved, but it has long-term implications for how America is governed. And that's truly historical.