David Hallowell, a spokesman for Mozilla, told ZDNet UK that there have been improvements to performance, security and the GUI since the preview release as well as work on native language versions of Firefox.
"A few improvements have been made to the interface and a lot of work has been put into localisation so more people will be able to use Firefox 1.0 in their native language," said Hallowell.
The preview release of Firefox was available in 12 languages, while RC 1.0 will be available in up to 24 languages including additional European languages such as French, German and Dutch, according to the SpreadFirefox Web site.
Hallowell said that RC1 is a test version to ensure that there are no problems with the bug fixes which have been made.
"The main purpose for it is to iron out any regressions caused by the bug fixes made since the preview release," said Hallowell. "Regular users are advised to wait until the Firefox 1.0 final release, expected around 9 November."
The preview release of Firefox has already attracted a great amount of interest. It beat its initial download goal of one million downloads within six days, and passed the five million download mark last week.
Bart Decrem, a member of the Mozilla marketing team told ZDNet UK last week that Firefox is increasingly being downloaded by consumers, but there are also enterprise deployments, including the City of Munich which has moved around 10,000 users to the browser, in the first step of its much talked about desktop Linux migration.
Firefox developers have not just had success in terms of downloads, but by the end of last week had managed to raise over $100,000 to fund an ad in the New York Times.
Firefox's ambitions don't end there. Mozilla has revealed that it expects one in 10 Internet users to be browsing using Firefox within the next year.
At the time of writing, Firefox 1.0PR had a 99 percent approval rating from over 450 ZDNet UK readers. You can download it and rate it yourself here.