No surprise there. There was a consensus opinion just about everywhere that Hillary would beat Barack in PA.
What matters is the margin of victory for Clinton.
Two months ago, Clinton had a 25% lead in the polls. This morning at 6AM, the margin was roughly 10%, with Clinton at 55% and Obama 45%. There are 158 delegates up for grabs tonight. If I extrapolate the current results to delegates earned in PA, we get approximately the following numbers:
Clinton 87 delegates
Obama 71 delegates
That will net Hillary a 16-delegate increase. She currently trails Obama by something like 140 delegates. She'll probably gain a few more super delegates also.
In two weeks, we have North Carolina and Indiana. NC has 115 delegates at stake (not counting supers); Indiana has 72. Obama is heavily favored to win in NC and Clinton not quite as favored in Indiana.
My guess is that the May 6th primaries will help Obama balance out any gains that Clinton makes tonight, leaving the margin roughly the same as it was going into tonight.
The North Carolina primary has an additional angle. John Edwards, the only other candidate who holds any delegates, and is a super delegate himself, has said repeatedly that he will hold his vote and endorsement until AFTER the primary, and he's hinted that he will follow the will of the voters in his state. If he does that, it's almost certain that Obama will get a significant bump in the delegate count after May 6th.
In any case, the margins will probably be the same or slightly bigger for Obama by then. The difference being that there will be about 300 less delegates up for grabs, and hope for a Clinton nomination will be more diminished.