Takes up some 4% of one core on my Core2 Duo Mac Mini with Safari. Which is entirely too much.
As I understand it this is a mis-appropriation of CSS3 and HTML. What really should be used for animating graphics is the HTML5 Canvas. After all the purpose here is resource generation, and not altering the presentation of a document.
Running Safari 4 on the mac and it runs great ;/ Thats whats annoying about this CSS stuff you never know if it will work. Hoping HTML5 will start moving forward.