Nice looking demo! Which version of Chrome is this though? It's perfectly smooth for me with the latest Chromium 6 code (svn rev 50635) on Gentoo amd64 arch - almost never dropping below 60fps. Running the current release of Chrome 5 on 64 bit win7 in VirtualBox I did get that slowdown, however the IE9 preview also slowed down considerably without GPU acceleration under VirtualBox. If that's also true running IE9 natively rendering on the CPU then the current Chromium code outperforms IE9. Even if that's not true, to be fair, a performance comparison between a pre-release version of IE and a current release of Chrome, FF, or Opera shouldn't be considered valid, especially if performance issues have been addressed in the latest development code.

 

These same effects look like they're probably doable using CSS transforms for an even smoother effect on those browsers which support them.