My opinion on Manning has evolved over time. When he was in college, I'm ashamed to admit I was in the Leaf > Manning crowd, as I thought Manning was too skinny and had happy feet. During his rookie year, I still though he was going to be lame as he threw a gazillion INTs, and Tee Martin won the national championship at Tenn (something Manning couldn't do).
But as I get older and wiser, I can appreciate what he has done and have to give him kudos for being an all-time great. He used to fun to watch (less so now with the lack of arm-strength and non-stop ducks he throws). He seems like a great guy, but I suspect his public persona is not a carbon copy of his real life (i.e., he's not as squeaky clean as the media likes to make him out to be).
He is an all-timer and deserves to be commended, but he does get an asterisk as he's shown that he isn't the best play-off or clutch QB (dating back to his college days).