A few points I would add:

The Obama campaign must be credited for showing organizational skills and tactical genius in the caucus states - or likewise the Clinton campaign must take some blame for inexplicably neglecting them. One of the great stories of this election is how a largely unknown 1st term senator somehow managed to out-organize and out-smart the most powerful political machine in the country in these crucial small/midsize state caucuses. This was one of the keys to his success in amassing sufficient pledged delegates to offset Clinton's success in big state primaries.

Clinton was badly damaged, right from the start of the campaign, from her initial support of the Iraq war back in 2003. In all fairness, she and many other good Democrats had no way of knowing that the Bush administration's "weapons of mass destruction" argument would vanish into thin air, and that the war would turn out to be such a huge and costly disaster for the country, and for America's standing in the world. Obama's consistent opposition to the war, even before it started, made him look like a prophet and won him the support of most of the progressive (or left if you prefer) wing of the Democratic Party.

In several important ways, Barack Obama is entirely different from any political leader who has come before him in American history, and many Americans find his originality very refreshing and attractive. He's truly unique in background and in his nature, the son of an African man and a white woman from Kansas, a child raised overseas among Asians, a man who's become an eloquent speaker and an idealistic visionary, an African-American intellectual whose political and public service experience is just as ample as the others, but different in a fundamental way - it's LOCAL experience, and not at the national level. His years have been spent on the streets of Chicago, as a community organizer and a state legislator in Illinois, not in the halls of power in Washington. That's an important point on which there hasn't been much commentary, and it contributes to his image as someone new and fresh and original.