Besides the final edition of Firefox 4, Mozilla also published the first release candidate of Firefox 4 for Mobile. You can download this mobile edition of Firefox over here, it's available for Android and Maemo.
Our Release Candidate is a very important step towards our final release. Since the previous (Beta 5) version, we improved performance even more, and we fixed numerous bugs and added some important features. Based on all the great user feedback we have received, we have continued to focus on making the browser faster, more stable, and more usable with this version.