Just heard Tucker Carlson say on MSNBC that the McCain people think independents are breaking almost 50-50 Obama/McCain. (Slightly more to Obama, but not much more.) I'm a little skeptical. But if true--and, even if it is, remember it's still pretty early in the day--that would be great news for McCain, and slightly below expectations for Obama, though probably not enough of a drop-off to really hurt him.
Also, keep in mind that if turnout among independents surges well beyond expecations, even splitting them 50-50 with McCain will yield Obama a huge absolute number of votes. So on some level the McCain-Obama split matters a lot less than overall independent turnout.