Well, first you get to rethink your idea and ask yourself" WTF is wrong here?" Then you start tweaking it here and there, making it simpler (but better) and a few months later you find that maybe the original idea wasn't all that, and the current one is more solid. Now you have been working hard to make the necessary changes and you are going to launch this Fall.
BTW the letter hurts.
I'm sure it all varies by degrees, situation by situation, but the idea isn't the point - ideas, as has been repeated ad nauseam, are everywhere. Recognizing opportunities (the factors that make a team predisposed to excel where others with the same idea would not) is much more valuable. A large (possibly larger?) part of the equation should (must?) be team-specific. From everything I've read, the idea will change in the YC process (as it should), the team could drop the original plan entirely and should still be strong enough to do something else better suited to their strengths.
It's hard to read "it's not the idea, it's the team" or "I don't invest in ideas, I invest in teams" and not want to prove someone wrong out of ego or passion/drive. It's difficult to appreciate the truth there without having realized it on your own, no matter how many times you hear that.
