Firefox 4 is now available for Android and Nokia Maemo devices in a new beta version which is giving great output in terms of stability and performance.
There are so many improvements and bug fixes are done from Firefox.
Some improvements include more pan/zoom responsiveness, faster booting and better page load times, the latter specifically due to JavaScript enhancements. The beta also includes features such as Firefox Sync (which lets you seamlessly carry your tabs, bookmarks and history between devices, whether those devices be mobile or desktop), tabbed browsing, Firefox add-ons and more.

Firefox for mobile is a developing area of the browser sector we’ve been following with great interest over the past year.
The browser originally launched with the codename “Fennec.” The alpha version hit the Android Market last August, and the first beta came out last October.
Unfortunately, iPhone and iPad users will have to stick to Firefox Home for iOS for now. The Firefox Home app isn’t a browser itself, but it will help Apple mobile users get access to their Firefox bookmarks, browsing history and open tabs — all from within Mobile Safari.
Expect more (and frequent) beta updates before a final tested-and-approved version is released.