Firefox 4.0 was officially released for both Mac OS X and Windows and let me tell you that it is a wonderful upgrade. I was actually testing Firefox 4.0 during its early beta phases so I got to become quite familiar with the new GUI early on; because of this the official release wasn’t as much as a surprise as it will be for when you update. However besides Firefox’s new GUI (Graphical User Interface), it features an incredible increase in speed over Firefox 3.0, and overall seems much more stable and reliable. I would say this upgrade is definitely mandatory for anyone who uses the Firefox browser.
If you are an avid Firefox user like myself let me know what you think of the upgrade in the comments section below!