The plain fact is that the JS engine in IE is, well, not the fastest JS engine out there. IE6, the extreme case, is just plain slow and old (and leaky, non-standard, etc). Take a look at the ‘All Library tests, to scale’ results at taskspeed for example.
Chrome Frame enables pages to be rendered in IE using the V8 Engine instead of the IE engine. This can yield significant performance improvement in IE and for 6.1, we’ve made it easy to use install and use GCF in your app.
A friend of the community forwarded me this graphical representation of putting the V8 into IE that was just too good not to share. 🙂