I just found this from TheVerge, very interesting part starts at 0:45sec.
http://www.youtube.com/watch?feature=player_embedded&v=Wy1dLr0g6Yc#!
"We only had a limited amount of time to test performance, but the 13 only hit 50 percent CPU utilization when we played the 1080p Iron Man 3 trailer while simultaneously playing back a multitrack GarageBand file and scrolling around a 21-megapixel RAW file in Aperture. That's impressive - and very encouraging considering the relatively weak Intel HD 4000 integrated graphics."
http://www.youtube.com/watch?feature=player_embedded&v=Wy1dLr0g6Yc#!