Mike Shaver, vice president of engineering at Mozilla, said that, barring any critical bugs, this version will be the one that gets rolled out to users.
Firefox 3.5 is available in over 70 languages, and includes more than 5,000 enhancements to Firefox 3, ranging from simple text changes in a dialogue box, to major modifications to the JavaScript engine and support for HTML 5.
Shaver highlighted the huge performance improvements, quoting Sunspider benchmarks showing the new release to be more than twice as fast as Firefox 3 and 10 times faster than Firefox 2.
The developers had split the focus into five areas: speed; user experience; security and privacy; customisation; and developer tools.
Firefox 3.5 includes a private browsing mode, which prevents any information from that session being recorded, and Mozilla has introduced several features which can do the same thing retroactively. So, rather than having to delete the entire history, cache and cookies, users have the option of 'forgetting' a single site, or clearing all data from the past hour or several hours.
Other major features include location-aware browsing, better video embedding, improved session restoring, basic image enhancement from within the browser and greater customisation options.
There are more than 6,000 add-ons currently available for Firefox, and the company has improved the categorisation and search tools to help users find the applications they want.
Mozilla also announced the launch of 'Collections', which allows users to group certain add-ons together, and find associated applications with ease.
Full details of the new features and improvements can be found on the Mozilla developer blog.
Those already running the beta version of Firefox 3.5 should receive the update automatically, or can upgrade manually by checking for updates within the browser.
Firefox 3.5 RC is available for download from the Mozilla site but does warn that, although very nearly ready for general use, this is still a release candidate and is intended for developer testing and community feedback.