Google hopes that delivering Chrome's rendering engine in an IE plugin will provide a pragmatic compromise for users who can't upgrade. Web developers will be able to use an X-UA-Compatible meta tag to specify that their page should be displayed with the Chrome renderer plugin instead of using Internet Explorer's Trident engine. This approach will ensure that the Chrome engine is only used when it is supposed to and that it won't disrupt the browser's handling of legacy Web applications that require IE6 compatibility.
Installing a plugin is arguably less disruptive to users than migrating them to a different browser. It is unclear, however, if IT departments that refuse to upgrade their users to a better browser are going to be comfortable deploying new plugins.