Penn State at the time was reeling from one of the worst scandals in the history of college sports (possibly the worst), the program honestly should have crumbled into nothingness from that point forward, but O'Brien not only kept them afloat but had winning records. I wouldn't say that was simply "ok," I actually think he did an amazing job given the circumstances.
I'm not saying O'Brien would be the answer at Nebraska, but I'm surprised that some of the extreme negative reactions in this thread against him. Meanwhile we have threads promoting guys like Lane Kiffin who has failed his way out of A LOT more jobs than Bill O'Brien and is a bigger d-bag, and other guys who have the stink of scandal on them like Ed Orgeron (Title IX lawsuit) and Hugh Freeze (recruiting violations and escort services). I'd take O'Brien over all those guys for sure.