Better late than never, Mozilla just launched the first non-beta version of its 64-bit Firefox browser for Windows. You can get it over here but be aware you need Windows 7 or higher. Additionally, plug-in support is still limited.
Today we are releasing Firefox 64-bit for Windows to offer gains in performance for users with 64-bit systems. We’re pleased to offer it to users of Windows 7 and above looking for added performance for applications and games.
Firefox 64-bit for Windows, by design, has limited support for plugins and users will notice that certain sites requiring plugins that worked in previous 32-bit versions of Firefox might not work in this 64-bit version. As we’ve shared previously, Mozilla intends to remove support for most NPAPI plugins in Firefox by the end of 2016.