Scalia, writing about Stevens' separately written opinion says:
Purer expression cannot be found of the principle of rule by judicial fiat. In the face of Justice Stevens' experience, the experience of all others is, it appears, of little consequence. The experience of the state legislatures and the Congress-who retain the death penalty as a form of punishment-is dismissed as “the product of habit and inattention rather than an acceptable deliberative process.” Ante, at 8. The experience of social scientists whose studies indicate that the death penalty deters crime is relegated to a footnote. Ante, at 10, n. 13. The experience of fellow citizens who support the death penalty is described, with only the most thinly veiled condemnation, as stemming from a “thirst for vengeance.” Ante, at 11. It is Justice Stevens' experience that reigns over all.
Orin Kerr, apparently, concurs:
The Stevens concurring opinion is certainly a throwback to an earlier age. I think Scalia's response was devastating, as the Stevens opinion does seem remarkably uninterested in distinguishing good policy from what the Constitution demands. Perhaps the most puzzling line in Stevens' concurrence was his statement that the Supreme Court's decisions "retain[ing] the death penalty as a part of our law" have been "the product of habit and inattention." The Supreme Court is inattentive to the death penalty like college guys are inattentive to women and beer.
Couldn't have said it better myself.
I guess that's why I just linked it.