He was an undergrad while I was in grad school at Stanford. I regret not going out on the golf course to see him play. He'll be not only the greatest golfer in history but one of the greatest competitors of all time.
His best competitive weapon is his mind. His will to win, sheer determination, and the love of the game enables him to work harder than anyone else.
He's a true student of the game - understands every aspect of the game (including its history) yet constantly strives to get better and better.
He doesn't take foolish risks (like Phil M). He protects his leads. He won't beat himself. But he's willing to take big risks in order to get better. He's remade his swing twice after unprecedented success. He's not willing to stand still - believes that if he's not getting ever, he's getting worse.
A humble winner and a gracious loser. Even a Tiger Woods won't win every time. But it won't be for lack of trying.