I think that was more a product of Dick Lebeau's defensive scheme giving Manning problems. He had a great gameplan and it was evident that Manning struggled with it; he said as much after the game.
I think that's what impressed me more than anything else: the Colts struggled offensively, yet still beat one of the NFL's top teams. Sure, the Steelers didn't play very well, but the Colts didn't "have it" last night and still got a convincing win. They are mentally tougher this year than in years' past, and that is why they'll win the Super Bowl.