If I have any app (other than Safari) maximized to full-screen, and then I move my curser up to trigger the menubar to show up, there's this weird animation. Like a white bar or something pops up. Maximize the App Store, then move your curser to the top of the screen to trigger the menu bar, and you'll see what I mean. In Safari, it works normally. The menu bar slides on down without any weird animation.