Mozilla has officially released Firefox 11, bringing a number of improvements, including the ability to synchronize add-ons across computers, improved compatibility with Growl, and several new developer features to help pages load faster. The update comes just 6 weeks after the release of Firefox 10.
From the official Firefox blog:
Firefox for Windows, Mac and Linux adds new in-product developer tools that make it easier to visualize page elements. Firefox also expands Firefox Sync capabilities to let users sync add-ons across computers.