The first and last animations are jumpy in my browser (Chrome 5.0.375.29 beta on OS X Snow Leopard), almost as if the last 20% of the frames are being skipped. The Facebook-style and three-dot animations are also off: The last two dots are synchronized nearly synchronized.
Is this a browser bug? If so, CSS3 throbbers aren’t ready for prime time yet.
Reloading the page seems to greatly reduce the visual bugs.