It allows web developers to take advantage of this feature, but still have their sites be accessible by people using IE (out of ignorance or otherwise). Right now no web-developer can really target features not available on IE unless they want to alienate a large percentage of their user base.
As a professional web developer I can say that is complete rubbish. We can not rely on most IE users to have this plugin so we can not take advantage of any new features. The fact is that while IE is as prevalent as it currently still is we have to develop primarily for that platform. In the corporate world a great many people still use IE6 so we have to test under that very thoroughly too.
The plugin will be very useful for intranets where IS the standard. So yes, it will help web developers for Intranets.
Wasn't there something about a PASCAL programmer knowing the value of everything and the Wirth of nothing?