I was reading about this release on the firefox forums. Apparently its not an official 1.0 RC1. It is a nightly build that just changed the version number for some reason. Sites took that as being a new stable version, when it isn't. Official stable builds will be on
http://www.mozilla.org/products/firefox/
edit:
http://forums.mozillazine.org/viewtopic.php?t=106431 shows a bit more