Depends on how you define 'integral' i guess.
But he's capable of being 1 of 4 central midfielders in a title winning
squad.
He gets a raw deal, and always has done, he's far better than the joke he's often been portrayed as. He's been a victim of the situation, and there's always a focus on what he CAN'T do over what he can. On who he isn't(Roy Keane) rather than who he is.
Put him in a functioning team where he can concentrate on breaking up play/hustling/closing space and carrying the ball forward from the defensive third and i think he's fine.
Don't get me wrong he's had a few stinkers, but he's a decent player on form.
I will admit i'm maybe a bit biased though as i've always had a soft spot for him.