The Firefox 29 Aurora release came in the same week as the mainline Firefox 27 browser debuted, providing users with fixes for 13 security advisories. The new Australis user interface in the Firefox 29 Aurora release has been making the rounds in the Firefox Nightly release channel since at least August 2013.
At the time, the expectation was for Australis to debut by the end of 2013. The Australis interface is a uniform overhaul of the core Firefox browser user interface across Windows, Mac and Linux desktops. The tab design is more rounded, and the users have more interface customization options. A primary difference is the User Menu system, which moves to the right of the browser window in the Australis update.