Contrary to the poll cited yesterday, this poll (it is my understanding that this is a Gallup Poll) finds much weaker support for Miers than Roberts, both among self-described conservatives and self-described moderates. Liberals generally dislike both, but if anything they slightly prefer Miers. Significantly fewer respondents express an initial positive impression of Miers than Roberts. Moreover, her status as a woman generally does not make respondents more likely to support her (most respondents say it makes no difference). By contrast, respondents indicate that they are less likely to support her in light of her being a close friend of the President, her "stealth" views on issues, and her lack of prior judicial experience.
Jason Sorens in the Comments points me to a Rasumussen poll that shows support for Miers falling. According to that poll, only 48% of Republicans say she should be confirmed and only 20% of Democrats.