Steven Suh has a great post up about what's wrong with McCain.
McCain would be just as clueless if he was 30 years younger. He'd be just as much of a jerk - he has been just as much of a jerk - no matter what age he's been. He was whoring himself out to lobbyists and corrupt businesses long before he reached the age at which it's ok to make fun of him. John McCain didn't live up to his own rhetoric decades ago. He has not only reversed himself on issues, he's done so on issues that supposedly define him as a human being, not just a politician: torture and detainee treatment, civil liberties, the power of the Executive Branch, proper American foreign policy, immigration - to call what he's done "flip-flopping" would be a grevious deception, because the truth of the matter is that he's a moral coward, a liar, a convictionless freak of America's dangerous right wing who, if anything, will actually make matters worse for this country than George W. Bush has.
That's John McCain, that's been John McCain, and it will always be John McCain. His age has nothing to do with it; therefore it should have nothing to do with us.
I, for one, won't be dumping on McCain's age. He'd be a terrible president at any age.