Young huskerj12 and present-day huskerj12 both think Callahan was a pretty poor head coach and a truly awful fit for NU.
My theory is that people now look back on Callahan with rose colored glasses because A) we have fluctuated between decent/mediocre and absolutely awful and no coach has broken through, and B) he was having recruiting success during a time when Rivals/online recruiting coverage was new and fun and exciting. They think Callahan was unfairly judged, but they really just miss the rush they felt following recruiting while he was the coach.
He’s also become sort of a symbol in peoples minds of the “anti-tradition coalition,” a guy who came from the outside and had to battle the crotchety old timers who have been holding us back all these years. Unfortunately he just wasn’t a good head football coach. The offense wasn’t great no matter how many times people claim it was "putting up great numbers." It sputtered constantly, was notoriously hard to learn and execute, I remember MANY games when it was a disorganized mess, and many more when we only racked up points/yards after we were already dominated. The defense fell off a cliff, he wasn’t an effective leader, he didn’t seem to connect with players/fans/UNL/Lincoln/Nebraska, it just wasn’t right and that’s ok.
I do think now looking back that he took extra heat for being the "first" crappy coach, and sadly many things that he got drilled for have become commonplace since he was fired. However, our incredible history was MUCH more recent (and useful) in those days, so the downfall felt completely insane. Throughout all the woes of the past three coaching tenures, I have never once looked back with regret about Callahan getting fired. He was never the answer.