I don't know much about Harriet Miers, but what little I do know, I don't like. First and foremost, she appears to be a hardcore W crony. Secondly, she has no judicial experience. While there have been, apparently, 39 appointed (or nominated, I forget), including Rehnquist, to the Supreme Court, I doubt they have been appointed by the likes of W.
Political games aside, I would dismiss her out of hand, and I would have no problem with that. While I heard a rumor that she might be pro-choice, there really doesn't seem to be much to substantiate her position on anything really. While Roberts had tons of decisions out there, Miers has comparatively nothing except for the support of W.
An anti-W friend of mine had a lot to say in support of her nomination (but not appointment), including her age (she'd have to retire before too long), that it would further build the case for W's cronyism, and that she would supposedly vote for pro-choice under a Rowe v. Wade type case.
Who knows? A lot of information could come out about her in the next few weeks.