As for the rest, only concern I have about Marrone is the comment someone else (Buffalo OC?) made that Marrone is too conservative with his playcalling/game management, and the team didn't go for it enough in critical situations. Not that I want a reckless riverboat gambler running the show, but the suggestion I got was that he (Marrone) lacks a feel for those moments when the game hangs in the balance, and tends to shy away from the bold initiative that can turn/clinch an outcome. No idea if that's true about him, but it's definitely a characteristic I would want to know about.
My personal view about coaches is that the great ones are very good at the details and preparation stuff, but they also have a patience and killer instinct for in-game situations. Rex IMHO lacked both those qualities but (almost) made up for it with his uniquely inspiring personality-based leadership style. He invariably made the wrong choice with respect to challenges (the borderline calls), and got burned often with his predictable 3rd and long blitz calls. As for preparation and details, well, the penalties and brain farts we too often saw were a product of that.
Marrone seems by all accounts to have the details/preparation thing covered. I don't want an accountant/drill sargent as head coach, however. If he inspires rebellion and discord, and lacks the killer instinct, his upside may be Mangini. We need a bit more than that.