It's sort of a trap as well as a gaffe; the gaffe part is that it targeted firefighters and police officers, who usually lean Republican, the trap part is that if the Obama campaign tries to highlight it in ads etc. they'll probably find it backfiring. Ordinary people are fed up with public-sector benefits, as we saw in Wisconsin.
Yes. I agree that Obama's campaign will try to use this as another way to snipe at Romney, but I don't see it hurting him in the long run. This race is a coin toss, but I give the edge to Mitt.