I'm not concerned about the character issues, but I'm interested to see how he reacts the first time he gets a 95 MPH fastball blown by his ear for his antics. Regardless though, he is the best talent in the draft, I agree that picking him is a no brainer at this point.
I think the herion addiction route is pretty rare. I'd be more worrid about his skills maturing (always a risk), than his attitude. In football a high first rounder can sign one contract and have a reasonable expectation that that will be the largest one they will ever see. In baseball, the number 1 over all may get a $10 million signing bonus, but they will make more than that over the course of their arb. years if they keep on working, and the big reward may be a decade off, i.e. there is a lot less incentive in baseball to be Ryan Leaf.