When the #1 QB in the nation wants to come to your school, you take him. Case closed. Arguments about whether or not we really need him are silly.
It's possible that Kiel didn't like the look of our depth chart when ND was seriously courting him preseason, but look at it now from his perspective: Crist is finished, Rees doesn't have the physical tools to hold him off, Hendrix is a project, and Golson is a complete mystery. If I'm Kiel, that depth chart looks much more inviting now than it did two months ago.
And for the record, I think the younger QBs (even Kiel, if he comes) will have a helluva time winning the starting job from Rees. But I seriously doubt Kiel sees it that way.