How viable is ie7-js by Dean Edwards?

I just found out about ie7-js ;

IE7 is a JavaScript library to make Microsoft Internet Explorer behave like a standards-compliant browser. It fixes many HTML and CSS issues and makes transparent PNG work correctly under IE5 and IE6.

http://code.google.com/p/ie7-js/

It looks like it's really good, but is it really working (the current issue list looks quite scary)? Have you already worked using this with success?

Another question is how slow the script will make the website in IE ?

From stackoverflow

• I think the best answer is: try it on your website and see if it works for your particular code. If it works, and doesn't impact the speed, great, you're done. If it doesn't work, then you're going to have to spend the time to make your site work in IE.

• In static pages it works pretty well. If you designed a couple of static html pages using modern browsers and standards and want it to be shown correctly in IE6 and 7 this script is gonna help you.

  But, and it's a big but, if you add a little javascript to the recipe, this method shows its weaknesses. Anything added later to them DOM or any event triggered afterwards will NOT be affected by this script.

  That's it. my one line recommendation is if you have simple and light pages use it. otherwise try solve your problems by looking at the roots!