Over on the Volokh Conspiracy, my friend (and fellow Dartmouth trustee) Todd Zywicki comments on Roberts and Miers. The money graphs:

There are two possible ways to think about appointments: one is to appoint those who will simply “vote right” on the Court, the other is to be more far-reaching and to try to change the legal culture. Individuals such as Brandeis, Holmes, Warren, all changed both the Court and the legal culture, by providing intellectual heft and credibility to a certain intellectual view of the law. Thomas and Scalia have been doing the same thing for some time now, with their view of the law….Rehnquist, by contrast, may have changed the voting patterns of the Court but did not change the legal culture through intellectual leadership. Even worse, pick someone who supposedly “votes right” but has no developed judicial philosophy, and soon you have someone who doesn’t even do that (Blackmun, Souter, etc.).
Bush’s back-to-back appointments of Roberts and Miers is a clear indication that his goal is at best to merely change the voting pattern of the Court rather than to change the legal culture.