The reason why Manning has done so well this year is because he calls the offensive plays. It was the same thing when Kelly ran the KGun offense. Manning has talent just like every other player in the NFL. He has a solid arm, and the intellegence needed to manage his offense.
Manning himself has said that the reason why the offense is so explosive is because of this. Manning is the master of his offense but he it is more of a committee. In an interview he says his playmakers (Harrison, Stokley, James) give him a ton of input. Harrison will flat out tell peyton in the huddle that he can beat such and such player.
I would be curious to see if Bledsoe would be able to call his own plays.