Obviously I don't think Romney has a snowball's chance of coming within sniffing distance of winning the general election. He just doesn't have a strength, Obama's even got him beat "in the case of a terrorist attack", IMO.
But based on very limited exposure (I haven't really been paying attention), I'm impressed with the agility Romney has shown in throwing counterpunches. Obama went after his wife for not having a day job, he was taken down a peg for hating on women. Obama went after him for disrespecting a dog, he was called out for eating dogs. etc.
Other Republican candidates of the last 20 years or so have always stood around and absorbed the charges, whether true or false, for a few weeks before deciding if they wanted to retaliate. This is different. Or else Obama has just picked terrible battles so far.