My sister recently bought the latest Macbook Air 13" with the 320M GPU, standard edition with 2gb of ram. I noticed that all the OS animations are choppy, spaces, exposé, even stacks. She hasn't really noticed it that much, but to me it's extremely annoying, and I want her to have a perfect Mac experience. Most noticeably was when playing a video with iMovie, when you move the mouse the video controls move into the screen from the button, that was extremely choppy, and made the video itself choppy too. I'm a little confused since I have a Macbook Air 11", and I have no animation choppyness. I'm a bit worried that something might be wrong with hers, maybe a faulty GPU? Is there a way I can check if it's functioning properly? Or fix the animations in some other way? Should I get it replaced?