He's run an epic campaign.  His ground game is bigger and better than anything we've seen in the history of US politics.  Likewise his money raising machine.  He's stayed (mostly) positive, even in the face of some pretty vile campaigning from Palin and McCain.  He responded far better to his opponent to the defining crisis of the election season (the wall street meltdown), and skillfully managed the Reverend Wright controversy.

It's no accident that he defeated one of the most fearsome political machines in modern politics (the Clintons), and is on the verge of defeating the other (the GOP) - he's simply run a better campaign than everyone else.

Finally, given his youth and relative inexperience, running a tight campaign over the course of two years is more than just an operational achievement - it gives confidence to independent voters that he is ready for the big stage.

And then there's the public speaking.

I don't know how his presidency will turn out - I am cautiously optimistic, but have concerns about having a liberal president + a liberal congress, as well as some of his more populist policy proposals.  But he has run a masterful, epic campaign during a grueling two year run.