Not to be a buzzkill, but the next question is obviously whether Obama will be able to get anything "big" done. That turns on lots of factors, but two big ones are the Senate races and the nature of his popular victory (i.e., is it a blowout? will politicians feel pressured to follow him?). On these last points, there is some cause for concern.
The Senate in particular is going to limit Obama's "big" agenda. It looks like Franken's going down. Plus, and rather shockingly, Alaska's going to send a convicted felon back it seems. And I'm not holding out hope for Georgia. At best, it's a runoff, and then he loses by a lot without the Obama wind.
But the popular vote (while certainly good enough) is not as overwhelming as it seems. Basically, everyone should go read Andrew Gelman's post crunching some numbers. His takeaways show potential warning signs -- (1) the election was close; (2) Obama lost the white vote by a decent bit; (3) the red/blue map wasn't really redrawn, there was just a global shift of a few percentage points to the Democrats (see his post for more and for more explanation).
Look, I'm as happy as anyone. But it's looking increasingly likely that the GOP is going to have both the numbers -- and the political ability -- to mount successful filibusters. Hope I'm wrong about that though.
[UPDATE: On the other hand, and on a far brighter note, John Judis argues that Obama's election is evidence that much larger underlying demographic shifts are taking place (e.g., the majority, she's "emerged"). The "Joe the Plumber"/Palin constituency is shrinking, while knowledge workers and minorities are growing. Thus, the GOP has hitched its wagon to a demographically shrinking base.
Also, as someone pointed out in the comments, we have to remember that this victory (which included very traditionally GOP states) went to a black man named "Obama." So I'm done finding clouds for the time being. Now's the time to be happy.]