So Firefox 1.0RC1 is sorta, kinda, out (get it here). I say kind of because the main web pages for Firefox still point to the Preview Release. I don't know why. In any case, the RC1 fixes a couple of hundred bugs that were in the Preview Release but seems to have several regression errors (i.e., new fixes that break earlier fixes). Still, if you want the absolute latest version of Firefox, feel free to download the RC1.
Otherwise, if you can wait a month or so, the official gold code will be available. If you can wait even longer, you may want to wait for version 1.1, which will, hopefully, fix the worst of the bugs still left.
As usual, the thundering herds are at the trough so downloading may be slow, although, when I went in this morning, the file came down nice and fast.
Aloha!