It was a fantastic speech (there's a thread below on that), and I'm sure people will be analyzing it in depth for ages.
And yes, it's a historic campaign on so many levels (race, youth, rapid rise, grass-roots, use of internet, etc. etc.).
And yes, he's got charisma...
But what makes Obama so compelling to me, beyond all that (which is already so much more than so many other candidates who come our way), is that he is one of the few people who not only thinks "deeply", but SYSTEMICALLY.
Obama not only sees the problems in an interconnected way, but he works at finding solutions that will be systemic. And this is exactly where he is misunderstood (perhaps purposefully) by his critics, who see him adding on new programs to the old, as opposed to restructuring the system.
Systemic thinking is confused with simply thinking "big" (wanting more), and it is more concrete than simply saying "thinking smart".
In this campaign, no one could give domestic policy details like Hillary, no one like Biden on foreign policy details, no one spoke about poverty with more conviction than Edwards... but NO ONE demonstrated as clearly as Obama the ability to view the interconnectedness of the political, economic, social, environmental, educational, etc. etc. issues.
We also only need to look at the speeches of the 2008 convention to see how eloquent everyone else has become. Whether they benefited from any specific help from Obama's team or learned by example, I don't know. But I have never heard Hillary, Bill Richardson or John Kerry give better speeches than they did this past week. I didn't put Biden on the list, because I have heard other great speeches from him.
Now, I'm looking forward to the Pres. debates, but would love to see one between Hillary and Gov. Palin!