He's a great athlete and what I call a great "college player," but I don't think he's got the tools to be a great NFL back. He's too flashy for the NFL game, and doesn't have that tackle-to-tackle presence that even small NFL runners like Tiki Barber have.
I honestly haven't watched Reggie Bush enough to argue one way or another. He does seem to have the pass catching ability that helps running backs in the pros. I tend to think that QB's (i.e. Ryan Leaf) tend to always win the biggest disappointment in the draft award. Running backs generally make the transistion better.