My view (subject to possible revision as the process continues) is that the Senate should confirm Miers. Under all past standards, she is qualified for the position, and the suspicion that she may not be a true conservative does not constitute sufficient reason to oppose the nomination.
It may well be that, from a senator's perspective, this is the final and decisive question. That's why in an ideal world, the president would withdraw the nomination.
No chance of that, of course.