1. A large (but too long effort) to call forth the better angels of his countrymen.
2. The audience reaction was very weird, but the people cheering and hooting really, really wanted to like him and they thought that the cheering was what he wanted. They were trying to help. It is a reminder of the (sometimes latent) strength of Obama's bond with millions of Americans.
3. The speech contained implied criticism of the Paul Krugman's and Andrew Sullivans of the world. This was very smart, but also very politically convenient. Obama is especially strong when he can position himself as an arbiter above left/right debates. He knows that being seen as a bitter and disingenuous left sectarian would get in the way of implementing his agenda and conducting the other responsibilities of governing. He has greater self-control and depth of vision that Professor Krugman. Obama is also tougher than the big mouthed Krugmans, Sullivans and Clyburns of the world - though they no doubt have their uses for Obama. He is focused on winning rather than lashing out petulantly