Don't search for a "preview" release of Firefox 3.5 because you won't find it on the Mozilla website. But you can still grab a "Preview" release by downloading Firefox 3.5 beta 4 and then going to the menu: Help -> Check for Updates and you'll be prompted to install a preview version of Firefox 3.5 which is not quite a Release Candidate just yet, but it's somewhere up from the betas.This Firefox 3.5 preview release fixes some javascript and stability issues, better support for the audio and video OGG codecs and some other minor fixes.
The Release Candidate, meanwhile, is still slated for tomorrow, so this looks to be something like an almost-there nightly build.
