Not bad at all. I am slightly surprised considering the approval of his other Midwestern counterparts (Kasich, Snyder, Quinn, Walker) and that he wasn't hugely popular when he was running.
He's not a far right Republican out of touch with the state elected largely by accident like 3/4 of those mentioned there and he's not governing an ungovernable state that was going to be a mess no matter who ran it now like Quinn.
And while he wasn't hugely popular while running, I think Republicans failed to understand that he wasn't hugely unpopular either. He was bland and forgettable in the Senate sure, but that's not going to put independents into a rage.