I haven't read the opinion yet, but summary from SCOTUSBlog is that the mandate has been upheld under Congress's power to impose taxes for the "general welfare." Chief Justice Roberts joins the majority opinion. The entire statute, therefore, is upheld.
I'll have much more to say about this shortly, but assuming the initial summary is correct, this is a travesty. The "general welfare" clause adds no additional powers to the enumerated powers of Article I, Section 8. It is only since the New Deal case of Helvering, 150 years after the ratification of the Constitution, that the Court suddenly "discovered" an omnibus "general welfare" power. This decision destroys any remaining limits on that power.
SCOTUSBlog says that Roberts' vote "saved the ACA." If that's true, it's a major indictment of Roberts' jurisprudence.
The only non-travesty aspect, so far, is that the decision apparently limits the federal government's ability to coerce the states via Medicaid funding. That would be the first time SCOTUS ever actually limited a conditional grant program. But small consolation there.