They're about what you'd expect. O'Connor politely argues on the majority's own turf, disputing whether there is a genuine and consistent trend among the states to disfavor capital punishment for crimes committed before 18, and seeing an insufficient shift since the Court affirmed the constitutionality of the juvenile death penalty in 1989's Stanford v. Kentucky. "I disagree with Justice Scalia's contention, post, at 15–22 (dissenting opinion), that foreign and international law have no place in our Eighth Amendment jurisprudence."
Scalia, joined by Rehnquist and Thomas, smacks the majority:
Hamilton had in mind a traditional judiciary, “bound down by strict rules and precedents which serve to define and point out their duty in every particular case that comes before them.” Id., at 471. Bound down, indeed. What a mockery today’s opinion makes of Hamilton’s expectation, announcing the Court’s conclusion that the meaning of our Constitution has changed over the past 15 years—not, mind you, that this Court’s decision 15 years ago was wrong, but that the Constitution has changed. The Court reaches this implausible result by purporting to advert, not to the original meaning of the Eighth Amendment, but to “the evolving standards of decency,” ante, at 6 (internal quotation marks omitted), of our national society. [...]Let it be noted, however, that Scalia grudgingly admits "our modern (though in my view mistaken) jurisprudence" takes into consideration what the national consensus is; like O'Connor, he then rips the majority for seeing such a consensus.
Because I do not believe that the meaning of our Eighth Amendment, any more than the meaning of other provisions of our Constitution, should be determined by the subjective views of five Members of this Court and like-minded foreigners, I dissent.
My personal favorite part of Scalia's dissent, however, has to be near the end when he points out that the Court doesn't look to other nations in its jurisprudence regarding the right to trial by jury, the exclusionary rule, the right to abortion or the separation of church and state. Then it's time to whack O'Connor for using foreign courts as a metric of reasonableness.