Too early to tell, but he deserves time before people start seriously critiquing.
I know he doesn't have much experience, but because of last year, I think he deserves to be able to learn on the job. He seems to be growing. I disagree that he's stubborn. Game one he effed up not running enough, he identified it, and the next game he ran a lot more. Sometimes you're stuck with the personnel you have, so you don't have a lot of options. Game flow dictates things as well.
What we need to see is how good he is at working with Pace and identifying talent. Right now, statistically, Montgomery isn't looking too good. He doesn't do anything with the defense, so if the offense doesn't step up....we'll see how well he can hold the locker room together when the defense is tired of carrying the team...and certain offensive players are not getting the touches they want because of ineptitude.