I'm not so sure he'll be an outstanding RB. He's never been "the guy", meaning a guy that can carry the load when a team needs it. He'll be a guy that gets 15 touches a game (running & receiving). Whoever gets him had better be happy with that.
He's also a guy that, on just about every single play, takes the ball and runs outside, whether there's a hole between the tackles or not. It's not a matter of running to the outside when something isn't there inside, that USC OL dominated and there were consistently places where Bush could run inside. Instead he elected to run toward the sideline 7 times out of 10 (if not more than that).
He's spectacular in the open field, probably the most electric player I've seen. But he won't be hitting the corner in the NFL like he does in college. Running backs that can’t run between the tackles aren’t successful in the NFL. That in combination with the fact that he'll likely need to split carries with another RB makes me think that the team that drafts him very high might not be so happy with the selection a few years down the road.