I assume that many of the people who voted for McCain wish that he had been elected. Any other assumption would be foolish. Everyone hasn't secretly realized that you were right all along, and quietly modified their views to concur with yours.
Good Lord Brandon, you can have preferred that candidate X were elected and yet still be glad with candidate Y. Because he seems good too. Because you can see his virtues even if he wasn't your top
choice. Because you're impressed by his intelligence or the beneficial effect he's having on people's confidence. Or yeah, because you're proud to be an American at a time it is the first majority-white country to elect a black person as President.
Just because you think one candidate was the best doesnt need
to mean the other makes you miserable. You can be sure that Phoenix hasn't "quietly modified" her views to concur with ours, or that she still wouldn't rather have had McCain. But she - and according to the polls, many other independents and even Republicans too - nevertheless feels good about Obama right now.
True, myself I'm far enough to the left that I'd never be glad with any Republican. But most people aren't as far out as you or me, Brandon. Not even most Republicans or Democrats are. They don't see the choice as some binary good or bad, in black and white. So no, it's not "almost half" of Americans who are "unhappy" today.