As a non-gameday coach, I give him a A++. He's performed miracles in changing the Bills culture from losers to winners. Let me say that again: he's performed miracles in changing the Bills culture from losers to winners.
He's done an above average B+ job during the week in preparing for an opponent.
On gameday, I score him a B grade. He's just OK with timeouts and challenges etc. He's no Bill Belichick on gameday.