Internet Explorer 9 final will require Windows 7 SP1 -- Update: no, it won't.
However, it's been decided that you're going to need Windows 7 SP1 installed before you can pop in the final version of IE9. Microsoft has yet to announce release dates for either SP1 or IE9, of course, but it's safe to assume that the service pack will arrive first based on the TechNet posting where the SP1 dependency is called out.
Why the hook to SP1? Will IE9 leverage some super-secret awesomeness that Microsoft has kept hidden from prying eyes? Probably not. But if you're going to run a shiny new browser, why not run it on the most up-to-date version of your OS that's available?
Interestingly (or not), there's no mention of Vista in the post. Of course, Vista users ought to either have installed Vista SP2 by now or upgraded to Windows 7 anyway, right?
[via Ars Techncia]
Microsoft has been reaching out to various sites to shed some light on the situation. In reality, SP1 will not be required:
"Internet Explorer 9 will work on Windows 7 RTW and Windows 7 SP1. When you install Internet Explorer 9 on a system that has Windows 7 RTM installed, additional operating system components are included as part of the installation of Internet Explorer 9. Those 'additional operating system components' will be part of Windows 7 SP1. Either way, this will be a seamless process for the user. Just wanted to make sure you had the latest."