“Experience the newest innovations in an unstable environment and provide feedback on features and performance to help determine what makes the final release.”
While informed users might find this silly, perhaps there is some data motivating Mozilla to inflate its version numbers, other than the fact that Google Chrome has already grabbed 20% of the browser market share, discretely updates itself, doesn’t brag too much about version numbers; and the fact that Internet Explorer is back in the race with version 9 that greatly improved performance and features.
In any case, Firefox 7 is said to bring with it some new features, including faster startup time, better rendering performance, and more importantly, lower memory footprint. It also features better font rendering when GPU acceleration is enabled. An improved Sync manager syncs bookmarks and passwords instantly with your other devices. Firefox 7 Aurora (alpha, 7.0a2) can be downloaded in a wide range of languages, and for Windows, Mac, and Linux, from this page. Aurora builds can be unstable and buggy.