Either way, this initiative is targeted straight at those users. We've heard from several sources that many corporate IT departments don't feel any need or urgency to upgrade, and receive very few complaints. We see this as a start -- the more complaints the IT department gets (especially from on top), the more pressure they'll feel to upgrade. Even if they can't upgrade IE 6 due to legacy applications, they could always install a version of Firefox side-by-side and only use IE 6 for the legacy apps.
For the other subset of IE6 users (moms, grandmothers, etc), this will be a great notice to let them know that their web experience is seriously degraded, and that they should strongly consider upgrading their web browser.