That said, how in the hell can McCain honestly attack Obama's supposed lack of experience now?

I think Democrats need to be careful with this argument. You're conceding that experience matters, which seems to be advantage McCain. The obvious answer is that Palin is running for VP, not President. The office of VP was, up until Carter/Mondale a mostly ceremonial job. The veep went to state funerals, broke ties in the Senate, and waited around for the President to die. The Secs of State, Defense, etc were all more involved in actual governance. McCain and Palin could revert to that model. As long as John stays upright, no problem.

A better argument might be that this is a transparent, cynical hail-Mary to try and get the PUMA vote. Obama was accused of admitting his foreign policy weakness when he nominated Biden. McCain is apparently admitting that he thinks he's going to lose unless he takes desperate chances like this.