I live in Buffalo. I heard him speak weekly. His relationship with the players was legendary. As in... abysmal. His arrogance dwarfed Belichick's. Saint Doug. That was his nickname up here.
That being said, every single person who ever spoke about him said he was a tremendous coach. I describe him as very much like Vrabel and Belichick but with less of a personality.
Marrone once told people openly (by openly, I mean, like, at the podium during a press conference) that he was the best coach in the NFL and that they didn't know what they had in him.
Read this:
NY Jets interview Doug Marrone, and with Bills, the ‘average’ ex-coach rubbed many in organization the wrong way
He was angling for the Jets job WHILE he was coaching the Bills, and people believe it was because Pegula took over as the new owner. But then the NY Daily News published the article above that said his own coaching staff hated him because he constantly belittled them and that he was a control freak and a phony. One of those assistants got on the radio and let loose against Marrone after the assistant was fired. On the radio, they said that the source behind the attack on Marrone was an ex-GM who had Woody Johnson's ear, but no one knows.
I think his downfall is that unlike Belichick, Marrone has a really thin skin, and he wanted to be appreciated. He grew up poor in the Bronx. He hated criticism. But was eager to deliver criticism. So, kind of old school, but he has his antennas up for any criticism.