In the instant case, yes.
However, it's been clear for a while now that Federal Courts have been acting as if the AEDPA [Antiterrorism and Effective Death Penalty Act of 1996] doesn't exist. What the lower Federal courts have been claiming is that death is such an important issue that all state court errors, even during sentencing, and even when the defendant has stipulated to guilt on all charges, are "unreasonable." If that were true, the limitation on habeas in AEDPA -- clearly intended by a nearly unanimous Congress -- would be rendered a legal nullity.
The Court today established a precedent that not every error by state courts is unreasonable, and that the limitations of habeas intervention by Federal courts intended by AEDPA has real teeth.