Roberts writes the opinion for the majority finding that the punishment for the Universal Mandate was simply to pay a tax, and since the government has a wide range of authority over its power to tax, that the entire Affordable Health Act is upheld. However, this decision strikes a huge blow against expansive readings of the Commerce Clause, as it is also a clear 5-4 vote against this act under the Commerce Clause. The Obama administration spent most of 2011 claiming that the result of failing to acquire health insurance was not a tax, but a penalty, and it is so phrased in the law itself. But their lack of foresight there did not doom them as Roberts and the left wing of the court decided it was.
Politically this will be read as a huge win for Obama, but I disagree with that analysis. Polls are running slightly against Obamacare nationwide, and this will ad fuel to that fire. The very thing that saved the ACA, the taxing power, might be the most unpopular power of government. I would expect a backlash.