I had this discussion with myself some time last year, even before Obama won the primaries. Obama would have a huge effect on world perception of the US. As a semi old-school Marx style materialist/realist, I am not convinced that perception matters, but it is still nice when it shifts to what I think is a more accurate image of America.
A friend of mine said recently, it'd be nice to tell your grand kids, that you voted for the first Black US President. But otherwise, he like me is still mostly unmotivated to vote.
I also decided, when I had this thought some time last year, the same sentiment Kristof ends with: "Look, Mr. Obama’s skin color is a bad reason to vote for him or against him."
That logic takes away the main reason I have for voting for Obama. So I am still largely indifferent.
(Amusingly, in Kristof's list of countries led by minority presidents, he left out Peru's Fujimori, perhaps because Fujimori fled in ignominy.)