85% of Windows users do not have an alternative installed. Most just go with what they were given. You know this, so don't play stupid.
A sizable chunk of these people will be confused. Many of the rest will find important sites broken or their computer hung during installation.
My concern, and this is the last time I will say it, is with the vast majority of people who don't have the knowledge you or I possess. For something that is not truly a "critical" type update, it is wrong to make people take this while they are sleeping to awaken with a potentially confused mess.
I know I will wind up being called by friends or clients to fix the dang things. So does KoRn and a few other technical one in this thread.
Your attitude would be absolutely useless in an IT environment. I would have been the CIO firing your butt.
Those that have used IE all their computer lives are not going to feel as if they're forced to use IE7. To them, it's merely an upgrade to an aging browser. Hell, my parents still use IE 5.01, on a Windows 98 machine. It works for what they need, and they don't feel the need to upgrade.
I've told them to try Firefox, but they're content with Internet Explorer. No one forced them to switch, and it's their computer, and if they want to use Internet Explorer 5.01, that's THEIR CHOICE.