A week after a pre-beta version of Firefox 4 appeared on Mozilla's nightly developer build site, the browser has been released as a public beta.
The move to tabs atop the browser began with Chrome's first beta, which backtracked a bit, moving to a design with a window border over the tabs (though they were still on top of the menu). The design is good in that it leaves more space for the Web content, but it may confuse some users who are used to seeing them down below the toolbars.
Firefox 4 beta 1's new menu button may also confuse some people, since its function isn't perfectly clear. Another detail taking inspiration from Opera (and Safari) is Firefox 4's combining of the Stop and Reload buttons, which switches between the two functions depending on whether you're loading a page or not. The address bar now offers a switch to tab option when you start typing text from another page's URL or page title.
Firefox 4 beta 1 plug-ins such as Adobe Flash, Microsoft Silverlight, or Apple QuickTime are now run in their own separate process, which can prevent crashes in the event of an error. A couple of major benefits for users is that they'll no longer have to restart the browser to install extensions, and they won't be thwarted from starting the browser by incessant update messages whenever any extensions have new versions.