We're beginning a new phase of the battle over Obamacare—and the fact that we can continue to refer to it as a "battle" tells you something—one that in some ways takes on the appearance of an electoral campaign, with television ads, media events, PR stunts, and a universal assumption that the whole thing is zero-sum. If anything related to Obamacare goes well—like, say, people getting health insurance at affordable prices—then that's bad for Republicans and something they'll do what they can to stop.
What we have here is something truly unprecedented: an opposition party not just insisting that a significant government program was a bad idea, not even just hoping that in its implementation it doesn't work, but committing itself to actively working to make sure the program fails and that as much human misery as possible can be created along the way, so that eventual repeal of the program will become possible.
The Obama administration is facing a huge administrative task, laid on top of which is a challenging political problem. Try to imagine a government trying to build a new bridge, while all throughout their political opponents were not only telling people they'd die if they drove across it, but going out to throw rocks at the construction workers.
Nevertheless, the Obama administration seems to be cautiously optimistic about its ability to overcome the obstacles.