I saw Justin on a talk show around June complaining that people approached him in the streets and verbally accosted him for being so smug and arrogant in the ad.
He was very negative about Apple on that show, getting defensive and claiming he isn't necessarily an Apple fan.
In the ads that have come out since then, he seems to have lost his confidence and more charming positive manner. You might notice it in the opening statements when he says "I'm a Mac", but doesn't smile anymore and seems to be saying "I want to crawl in a hole and hide."
IMO, that has affected the quality of the ads.