Yes, Firefox 5 Beta has been released!
This release includes the Firefox channel switcher, performance and stability enhancements and support for the new CSS Animations standard to allow developers build more amazing Web experiences. The new Firefox channel switcher lets users move between Firefox Aurora, Beta and Release channels to test features at various levels of development, quality and polish.
You can download here for Windows, Mac OSX and Linux: http://www.mozilla.com/en-US/firefox/channel/
Here are some of Firefox 5 screenshots running on Mac OSX Lion


