With the release of Firefox 10 as stable version, Firefox nightly channel has got Firefox 13. The Firefox 13 is scheduled to release in June 2012.
At this moment, Firefox 13 Nightly has no visible new feature. We expect several features to be introduced with Firefox 13 including panel-based download manager, ability to clean up user profile, improved display of location bar results etc.
As UAC pop-up has been removed for Firefox updates, we hope to see full silent updates in Firefox 13 (or even in Firefox 12).
Another important thing about Firefox 13 is the end of support for Windows 2000, Windows XP RTM and SP1. Mozilla’s Asa Dotzler informs, “It’s always a difficult decision to leave some users behind. The number of Firefox users on those OS versions — less than one half of one percent of our Windows Firefox users […] If you are a Windows 2000 user, Firefox 12, released on June 5th, will be the final supported Firefox release.”.
The nightly builds are meant for development and testing purposes. Firefox 13.0a1 build can be downloaded from here for Windows (32-bit and 64-bit), Linux, Mac and Android platforms.