No one's position is verifiable before they assume a seat on the SC. Meirs was when the talking heads and a lot of shortsighted conservatives decided you could not trust GWB.
That might haunt the conservative movement for years.
That's true, to an extent. However, you are able to verify to a degree by examining rulings on lower courts and looking for conservative judicial opinions.
Alito had those - Miers did not.
You may be right - Miers might have been great.
But in a situation where you don't get a do-over (see Souter, David), you simply cannot take that chance.