updated 04:46 am EST, Tue February 19, 2013
Downloads made available earlier than official launch
Though no official changelog for version 19 has been made available ahead of its formal release, The Next Web suggests that the beta release notes would be a suitable guide to changes. Some changes in the way Firefox handles HTML5 CSS and developer-specific items have been included in the release, which appears to be ready for the major desktop operating systems.
Though Firefox 19 for Android went into beta at the same time as the desktop version, it is not clear if it will exit beta alongside the desktop clients. Google Play, at the time of writing, shows Firefox for Android was last updated on February 7th.