After all the testing, Firefox 3 Release Candidate 1 (RC1) is available for download from the Mozilla Web site. According to the development team, FF3 RC1 incorporates a slicker UI for Windows Vista, XP, Mac OS X and Linux, based on user feedback.
It is based on the Gecko 1.9 Web rendering platform, which has been under development for 33 months now, and which incorporates more than 14,000 updates including some major re-architecting to provide improved performance, stability, rendering correctness, and code simplification and sustainability.
A thing to remember: Installing FF3 will overwrite your existing installation of Firefox on Mac OS X and Linux. On Windows, Firefox 3 installs in a new folder. For all systems, you won’t lose any of your bookmarks or browsing history, but some of your extensions and other add-ons might not work until updates for them are made available.