There seems to be some impatience with this thread, so I'll be brief.
Your reasons 1 and 3 are really part of the same package. To isolate them is to ignore how the two complement each other. People know that Urban Meyer has led a similarly inexperienced squad to a championship before, so people don't, and shouldn't, discount his ability to do so again. As far as reason 2 goes, yes, there is faith in the talent fighting to earn a spot on the roster. However, for fans on this site, that talent is not a vague hope, or simply based on recruiting stars earned in high school. It comes through our fanatical observation of each player's development, and an understanding of how each individual fits the team. In other words, there are faces attached to the talent, and particular reasons to have faith in each.
Without getting into a long breakdown as to why, I'd say I expect the offense to be better this year, and the defense to be worse. I don't discount the challenge that others present to the Buckeyes. What is amazing to me is that many seem to be discounting the challenge the Buckeyes will provide.