Last night Mozilla released the first beta of Firefox 3.0. The beta is available for Windows, Mac OS X, and Linux at Mozilla’s download site in 20 different languages.
Remember that this is still beta software so don’t expect it to work flawlessly. Many websites and extensions don’t work very well with the browser.
The browser has seen many improvements on the features side but nothing that really seems to stand above the rest as a “killer” feature.
With some time the application will exit beta stage and undoubtably will work much better but for now I suggest you look at the release notes, maybe download it to try it out, but most likely you will end up going back to trusty old Firefox 2.