Fox News had Dan Marino says it can help you throw the ball a bit more easily.
http://video.foxnews.com/v/400208195...#sp=show-clips
I was willing to give the Patriots the benefit of the doubt until I heard it was 11 of 12 balls underinflated. If the ball is easier to throw, it is likely easier to catch. While it was not the only reason the Patriots won, it certainly didn't hurt... Until they got caught.