The stable version for Firefox 15 has been available for a short while, but Mozilla just launched it officially. The release notes, as usual, are almost the same as those for the beta, with some slight modifications.
Preliminary native support for PDF did not make it to the stable release and remained in beta (Firefox 16.0 beta 1 is scheduled to be pushed to users on Thursday).
At the top of the notes there are silent, background updates, which should cause future updating to occur seamlessly, except when the update process encounters an incompatible add-on; this should trigger a dialog with options for the user.
The developer also lists a set of four unsolved, known issues, among which crashing of the browser if you try to launch it with a locked profile.Download Firefox for WindowsDownload Firefox for MacDownload Firefox for LinuxDownload Firefox for Android