On the same day that Apple released the public version of Safari 4 for Windows and Mac, Mozilla published an update to its Firefox 3.5 beta. Available for Windows, Mac, and Linux, they're not calling this a beta version, but it's not a release candidate, either.
Within the next 24 hours, the Firefox 3.5 beta 4 will auto-update to what Mozilla is calling a "preview" version. Users can also force the update by going to the Help menu, then Check for Updates. At the time of writing, it doesn't appear that users can download the 3.5 Preview version directly.
In a press release, Mozilla said that Firefox 3.5 Preview will leverage the more than 800,000 users of the 3.5 beta to further test changes made to the browser, indicating that it feels the browser is fine for daily use but might still contain significant problems.
I also noticed that there's a minor interface change in the Preview. Tab management buttons are now gray on gray, changed from the green on gray.
Mozilla's open-source evangelist, Christopher Blizzard, is also highlighting the new developer features coming in Firefox 3.5 in a new blog.
The Firefox milestone announcement can be read here.