The New York Times has an interesting video analysis of Obama addressing the "experience" issue. They compare his argument from this past February to the one he made on the stump this week. You can see that he has become a much better stump speaker but you can also see that his argument is more nuanced. Props should be given to the NY Times for doing a bit more than horse race reporting.
http://www.nytimes.com/ and go to the Video link.