In the past, Internet Explorer has always been required in order to download certain updates or Microsoft programs. When installing the PDF and XPS plugin for Office 2007, I used FireFox by default not thinking that I might need to use IE. I was very surprised when I saw that I could validate WGA and download the plugin from FireFox. Here is a quote from the site:

"Some downloads are made available only after users have validated their versions of Microsoft Office. Firefox and Netscape Navigator browser users may install a helper program, the Office Genuine Advantage plug-in, to enhance their download experience."

Perhaps Microsoft is embracing the the competition and letting people choose their own browser. Unfortunately http://update.microsoft.com still requires Internet Explorer.