His tenure specifically at Michigan is. I still think regardless of what happens at Michigan, what he did at Stanford and with the 49ers was extremely impressive.
I think what really helped him be successful at Stanford was that he brought a big, physical, "mean" brand of football that the Pac 12 wasn't used to playing against. Even though he had Andrew Luck, they were a power running team the entire time he was there. What really helped him in SF was bringing the read option or read option concepts and it took NFL defenses a while to adjust to it.
At Michigan, he's basically going strength on strength - he's playing a stereotypical brand of Big Ten football in the Big Ten - and it isn't working out as well as anyone hoped. He's successful when he brings to something different to the table.