I think there's a legitimate argument that pulling out the way Obama is planning on could be more harmful to our country in the long run than staying until whenever the way McCain wants to.
The problem is that, much as McCain would love to dismiss the "How did we get here?" question, the fact that we shouldn't have gone in in the first place IS relevant to whether he has good judgement. He's said "the surge is working" enough times that it's become CW (and Obama and the rest of the Dems haven't had the balls to argue with him), but that claim is debatable at best.
I'm willing to acknowledge that we're fucked whatever we do in Iraq, and we're going to have to pick the lesser-evil path from here on in. I just disagree that staying in there is the lesser-evil path.
There's also the question of McCain's bellicosity on Iran. Even assuming he's 100% right on Iraq (which I of course do not), he's not a guy I'd trust with the decision on whether or not to start another war.
Per Concorde Fallacy (which, again, I'm not suggesting Bongo buys into, but since Lyrai brought it up), the "but if we leave, all those troops died for nothing!" argument is a very human, instinctive reaction. But it's not a rational one. For my part, I think the war has been a horrible waste and everyone who's died there has died because of the Bush Administration's lies, incompetence, and flawed worldview. And that's not a pretty thought to have; in fact it's heartbreaking.
But I think Obama handled it well in one of the debates when he said that no soldier ever dies in vain; service to your country is always honorable.
I think he's probably right in a certain sense, though my sympathy lies more with John Kerry (back when he still had balls): How can you ask a man to be the last one to die for a mistake?