He is the winningest coach in MAC history. Prior to him being hired, Ohio had gone to 2 bowls in their entire history with the last one being in 1968. Under his coaching, Ohio went to 11 bowl games in his 15 years (didn't get bowl invites the two years he went .500). He only had a sub-.500 record 2 times while he was there, whereas the 20 years prior to him coming there, they were only .500 and above 3 times. That is all beside his .750 winning percentage at Nebraska with a National title game appearance. I mean he is top 40 in all-time wins as a head coach.
Not sure why people still want to bash on him, as he was pretty obviously a solid football coach. He may not have been great, but he was still a good head coach.