I don't have a problem with Miers per se, it's just that we really don't know anything about her.
I am aware that Bush has known her for a long time, and I trust that when he interviewed her, he focused on her Constitutional philosophy. However, a lot of judges have been known by the presidents who appointed them, but once installed they have developed a "new" philosophy. A lifetime appointment can give judges the latitude to develop new attitudes or become intoxicated with their power. We need to remember that many of the justices who have torn this country apart were appointed by Republicans.