The majority of the users of my company's web application use IE6 on Windows 2000. Additionally, many of these computers have Vista stickers on them, and are quite powerful. Their IT groups already have established practices to support the machines, and they are used almost exclusively to surf the web and run software that was purchased 5 years ago. Our users aren't even unhappy, as their work does not center around a computer; thus, the corporate IT infrastructure has no motivation to upgrade them.
That said, we still pressure them to upgrade, and I'll be extremely happy when they eventually do.
perhaps instead of all these silly campaigns to try to force users to upgrade, they should make a simple questionnaire that asks the user why they are still using ie6, and then publish the results. i have a feeling the leading reason will not be "because some jerk in IT won't let me".