The major political significance of Obama's election to this point appears to be that it has helped to bring about the rise of the Tea Party in American politics. Obama is seen as enough of a big government liberal to motivate many people to move towards political opinions like those of the Tea Party. This is having a major impact on American politics and the politics of the Republican Party in particular.
Economically, I would argue Obama's election has had little or no significance. Presidents are not nearly as important in determining the state of the economy as people think they are. Obama has come into a bad situation that has not improved much. I do not believe, though, that it is his fault that the economy has not improved.