That is the line that has already made it into the AP story and the Washington Post. It was the one truly unscripted (or at least it seemed to be) line and the one real "ouch" moment IMO. Not huge, compared to "you're no JFK" bt not what Kerry needed to come from behind.
Perhaps it doesn't carry the political "zing" of the old "JFK" statement, but its message carries considerably more real-world weight.
BTW, I also liked how Bush flat-out told Kerry that his bilateral approach was, in no uncertain terms, very wrong.