Everybody's quoting Andrew Sullivan on this, because he nailed it:
It was a liberal speech, more unabashedly, unashamedly liberal than any Democratic acceptance speech since the great era of American liberalism. But it made the case for that liberalism - in the context of the decline of the American dream, and the rise of cynicism and the collapse of cultural unity. His ability to portray that liberalism as a patriotic, unifying, ennobling tradition makes him the most lethal and remarkable Democratic figure since John F Kennedy.
What he didn't do was give an airy, abstract, dreamy confection of rhetoric. The McCain campaign set Obama up as a celebrity airhead, a Paris Hilton of wealth and elitism. And he let them portray him that way, and let them over-reach, and let them punch him again and again ... and then he turned around and destroyed them. If the Rove Republicans thought they were playing with a patsy, they just got a reality check.
My favorite part:
But I stand before you tonight because all across America something is stirring. What the nay-sayers don't understand is that this election has never been about me. It's been about you.