Firefox 4 for mobile has one of the coolest feature like Sync, where you can sync your preferences, open tabs, history, bookmarks, passwords across mobile and desktop and the data is encrypted via a 26 character key. Other features include tabbed browsing, password manager.
You can share a page directly with a single click to facebook, Email, Twitter or save it as a PDF for offline use. Customize your browser and make it as you like using the Add-ons. Go play with it now!
In addition to the above features, Firefox mobile also supports CSS3 and HTML 5 ( can watch Youtube without flash installed ).
A website is specially launched to celebrate Firefox going Mobile, Spark, a game that challenges you to share with friends to help the flame of the open Web glow bright. Now, go and start the spark! It is just like the Glow website which was created for the release of Desktop version.
Firefox also noted that it is three times faster than the stock browser on Android. Check out the latest Web O' Wonder demos, you can even create one.
Overall Firefox 4 for Mobile is just Awesome! :)