JS library that makes IE5-6 render like IE7! No more IE6 hacks!

I was looking at another frustrating CSS cross browser issue where I wanted to change a style on the first list item using :first-child but of course IE6 did not support this. So I was looking at examples that set a class on the first item manually or by using jQuery but then happened apon the following:

Dean Edwards has created a JS library that makes IE5-6 render like IE7, so it fixes issues like png transparency, adds the ability to use :first-child and more.
He also has a different release which gives IE5-7 advanced CSS features missing from IE7 like :contains(), :nth-last-child() and more

His site
http://dean.edwards.name/weblog/2008/01/ie7-2/

see demos here
http://ie7-js.googlecode.com/svn/test/index.html