To summarize:
Registered voters
Before convention, kerry 49 bush 45
After convention, kerry 50 bush 47
Even THAT is good news. Kerry got a 1 point bounce from the convention among registered voters, but Bush got a 2 point bounce. That means of the people who were knocked off the fence by the convention, TWICE as many said "nah, not buying it. I'm goin' for Bush". And Bush wasn't even there to refute Kerry's PR! Incredible!
And it's even better for LIKELY voters, not just registered.
Likely voters
Before convention, kerry 47 bush 46
After convention, kerry 47 bush 50
So among likely voters, a much more reliable indicator than registered voters, for those who the convention knocked off the fence, NOBODY went for Kerry, and ALL OF THEM WENT FOR BUSH!
They can spin this any way they like, that's front page, nightly news leading stuff. So check the New York Times, CBS, ad nauseam, and see if it leads. But don't bet the farm.
Polls are polls, but delicious nonetheless.