Firefox 6 for Windows is 13.3 MB download and we can report that it works just fine. A few of our favorite web pages work like a charm and this includes this one you are reading. Firefox 7 is well under beta, and if Mozilla foundation continues at this speed, you might see the official version well before the end of the year.
You can download the Windows version here, and in case you need the one for other operating systems you can do a quick web search.
The official version via Firefox update should be available tomorrow, August 16th.