Tom Jensen says the result backs up PPP's polling:
NY-26's results are not occurring in a vacuum. Democrats had a 7 point lead at 47-40 on our last look at the national generic Congressional ballot. And Democrats have led the generic Congressional ballot on 7 consecutive national polls we've asked about it on going back to mid-February. Voters shifted sharply back toward the Democrats after just a couple months of Republican control of the House.
Nate Silver's two cents:
I don’t know that Mr. Obama is much more likely than a 2-to-1 favorite to retain the White House, nor that Democrats better than even money to take back the House. But both sets of odds have improved, in my view, from where I would have pegged them a few months ago.