A bit of googling around revealed that apparently no one else in the world has this problem, and I am an idiot. Then I happened upon a gem at stackoverflow.com which mentioned, in passing, that Internet Explorer does an awful job of caching and displaying background images (specifically repeated background images) during animation – basically, he implied that for each frame of animation, I.E. loads, places, and renders each instance of a repeating background image, just one example of how a browser could have issues with animations. The specific elements I’m working with are 1000 px wide rows, and with each animation, about 10 of them have to move 300 pixels or so. The kicker? Each one is using a 1px wide repeating background. 1000 background images * 10 rows, and it becomes apparent why the animation was so bad. I bit the bullet and tried a single 1000px wide background image, and the difference was night and day.