Just passing this along. The Mozilla website hasn’t been updated as of now, but my ff4RC updated today…as will yours if you participated in the beta testing program.
Still, it’s problematic…. doesn’t show the vids I can see with Opera 11.01 on WC. Neither does ie9.
For those interested (from Island Dog):
http://releases.mozilla.org/pub/mozilla.org/firefox/releases/4.0/win32/en-US/Firefox%20Setup%204.0.exe
Additional source reading: http://www.neowin.net/news/mozilla-launches-firefox-4