The Mozilla Foundation has released an open beta of Firefox 4 into the wild and is asking users to "help make the next version of the world's best browser."
The Firefox 4 beta, which includes a new Feedback add-on based on Mozilla Test Pilot to allow instant bug reporting, is available now for Windows, Unix and Mac OS X in various states of completion.
Based on the Gecko 2.0 Web platform, the version 1 beta is supposed to be stable and safe for daily browsing although the vast majority of add-ons have yet to be tested.
There are a few cosmetic changes to the layout of the browser with tabs now appearing at the top of the window a la Opera in the Windows version. Mac and Linux versions will also eventually be modified in the same way.
In Windows, the menu bar has been replaced with a Firefox button and a new smart location bar has been added.
The Bookmarks Toolbar has been replaced with a single button, but users can switch back to the old method if they want to.
Under the bonnet, CSS transitions are now partially supported and, although it has been disabled for this beta release, full WebGL support will be included in the final release.
Native support for High Definition HTML5 WebM video has been added as well as a new HTML5 parser and support for more of the new web standard's form controls.
There are a number of known issues with the open beta including some which may cause crashes but Mozilla is keen for users to give the half-baked application a go in order to iron out the bugs.
You can download the beta in its manifold flavours, and at your own peril, right here.