Yeah, I can see it's benefit for static navigation, headers, footers, etc...

I would use it for my site but the navigation header and such need to be dynamic depending upon which page is being shown. Is there anyway to pass parameters to these external file or are they pretty much straight html? Right now I call a javascript method at the beginning of my body that writes the header code to the document and depending upon which page "index" is passed in I set that page to selected in a drop down list.