I think that fact points to one reason for the disappointment. The unanimity came with an unstated assumption, that GWB would nominate a candidate in the mold of Scalia or Thomas. People mistook that statement, and right or wrong, don't see Miers as satisfying the promise of "in the mold of Scalia or Thomas."
Following that vein, not only is their disappointment with the nomination, there is also a diminishing of trust in the President - for a nomination where of of his stronger selling points is "trust me."
As I said, "right or wrong," but there is little doubt some party-faithful feel something that resembles betrayal.
I'm inclined to believe that Miers would render opinins that are acceptable to my sense of how SCOTUS should rule. But I am very unhappy with the pick.
Then I'm confused.