Although the official announcement is not expected until tomorrow, the final version of Firefox 4 is available on Mozilla servers. Here you can download the English version for Mac OS X.
* Firefox 4 for Mac OS X
With this launch Mozilla puts an end to development of many months and many delays. But the wait has been worthwhile and that the quality leap in this browser is quite important and places it at the front row of browsers. No doubt if you are regular user of Firefox, I recommend upgrading to the fourth version as soon as you can. And if you use any other browser I recommend you give it a try.