I'm using the ISAPI_FILTER for mod_rewrite. Here's my .htaccess code incase anyone needed it. I couldn't figure out the second condition so I left it out for now and just add additional file extension to the first condition.
Minh - are you familiar with downloading SilverStripe via subversion and then using subversion to create a patch file? It's a good way of discovering *all* of the little changes that you needed to make in order to get SilverStripe working on IIS.
I can help with the IIS installation documentation. But applying svn patch would not be possible because I don't have direct access to the Windows box that's hosting the site. So I couldn't get tortoise svn going. Unless you could think of another way.