With no disrespect intended to Ms. Miers, I agree that there are probably a thousand resumes more impressive than hers for this position, and if you are accustomed to thinking of America as a meritocracy, that's enough to generate some disappointment. Stepping back from that initial reaction, I think that Todd Zywicki provides a useful way to think about what her nomination represents:
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. This is, of course, precisely why Bork was taken down as well. 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.).
The opportunity that was lost was to help shift the Court through the intellectual argument. That's a fair point. The surprising aspect of this commentary, which is echoed in many places on the political right, is that there is doubt about Miers' likely voting patterns. Are you kidding? She has been on this President's staff for a number of years. How could anyone but a "Bush Conservative" tolerate that proximity for so long without having views that were wholly compatible? The conservatives have something to worry about in charges of cronyism, but I would be shocked to see a Justice Miers anywhere but in the Scalia-Thomas wing of the Court.