I just think that Manning has already proven he has a much better knack for talent evaluation and recruiting than you-know-who. He has proven he is much more personable and better at dealing with the media, fans and supporters. I think he has proven he is a better game coach - though he hasn't proven to be a great game coach yet, by any means. Clearly we are working from a low bar, but, I think these factors guarantee that the program is in a better position than it was under he-who-shall-not-be-named and is guaranteed to get better.
I am not saying we have seen certain evidence yet that Manning will lead us back to prominence - just that we will better than we have been the last 4-5 years.
The two nuggets of proof still to be seen are (i) the ability to land 4 and 5 star talent on a somewhat consistent basis - spotting and landing under-rated recruits is great and can serve as the base of a program, but, to reach a higher level you need to also be able to land some elite talent. And (ii) a more elite level of game strategy and coaching. This is hard to demonstrate without some talent and is harder to quantify.