IE 9 as a Windows Update: Is it fair?

IE 9 has been launched with generally positive reviews. But I find it a bit unsettling to find that Microsoft is pushing it out as a Windows Update. For one, isn't it a totally different program than IE8 or earlier versions? Second, the user may not be ready for it since his chosen Internet Security software (Mcafee, for instance) and favourite ecommerce sites may not yet be working with IE9. I would like to see some thoughtful answers from the experts at Hacker News.