Key features of Firefox 16 include a new developer command line to provide easy keyboard controls over the developer tools in an intuitive manner, unprefixing new stable features, and improvements to Firefox for Android.
Now deemed stable and unprefixed with Firefox 16 are CSS3 Animations, Transitions, Transforms, Image Values, IndexedDB and Values and Units. As additionally bonuses, the Battery API and Vibration APIs that were developed in part by Mozilla are also now considered stable.
For those curious about the Firefox Developer Command-Line see the video below or this Mozilla blog post.
Firefox 16 can be downloaded from Firefox.com for your favorite operating system.