Harbaugh is a very weird dude. He is a strong motivator for a short period of time and then he burns people out. That is why he is much better in college than in the pros; he needs turnover or they tune him out. Is he a proven winner? Not of any final prizes. No championships and not even a college conference title since San Diego. Having said that, I think he'll win a title at Michigan, but it will almost be in spite of himself.
He is his own worst offensive enemy. He loves to build his team around the quarterback (hard to do consistently in college) and he can't resist being cute and showing off his toys (see the centipede and those other bull**** formations last year?). The end result is that he doesn't develop bread and butter offensive plays. You beat Harbaugh's Michigan by hitting them in the mouth, keeping it close for a half, and letting them fumble around, trying to figure out what to do consistently. See Iowa v. Michigan last year for the blueprint.