Thanks for posting the interesting information on Marshall, of which I was unaware.
However, as mentioned in the article here, the criticism from conservatives disappointed by the Miers nomination has nothing to do with her lack of judicial experience. It goes to the absence of anything in her record suggesting she is well-informed or concerned about the major constitutional issues of the day, whereas W had a deep bench of brilliant conservative scholars and jurists that he chose to overlook.
There is nothing that you can point to that says she is not informed or concerned about the "constitutional issues of the day " (whatever the hell that means).
She is not a constitutional lawyer, which, BTW, is just fine, as far as someone like Antonin Scalia is concerned. So, naturally, she's not going to be babbling about the Constitution at every turn.
Wait for the hearings. We'll all get to decide then.