The latest Firefox 4 Mobile beta for Android and Maemo promises more speed and a fresher look, but it's still not ready to replace the default browser.
I haven't tested Mozilla's speed claims on my Droid Incredible, but I'm more concerned with the interface than the speed of loading individual pages. And Firefox Mobile has a lot of work to do.
Problems start with the URL bar. Like the stock browser, Firefox uses a single bar for Web addresses and searches. For some odd reason, this bar has a automatic spell correction. Think about how many URLs you type that aren't real words, and you can imagine how frustrating this becomes. (PCWorld.com, for instance, became just "World.com") The keyboard for entering URLs also lacks a ".com" button, adding more time to what should be a simple process. On the bright side, you can elect to search on Amazon, Twitter and Wikipedia with just a couple taps.
Firefox Mobile's distinctive sidebars also cause more problems than they solve. Slide all the way to the left in a Web page, and you'll see all open windows. Slide right, and you get forward and back buttons, a bookmark button and a link to the options menu. Unless the Website you're visiting is optimized for mobile, chances are you'll be scrolling left and right fairly often, which means you'll bump into these menus by accident. Firefox should just use Android's built-in menu button, like every other app. (It shows security information instead.)
As with the desktop version of Firefox, add-ons are one of Firefox Mobile's main attractions. There are some useful ones, like a low-quality Flash player, a find-in-page utility and a barcode generator. The problem is finding them. Firefox's mobile add-on page could really use some smartphone optimization, or more integration directly into the browser, so that hunting for great add-ons isn't a chore.
The best is yet to come for Firefox Mobile. The next beta version will have HTML5 support and hardware acceleration for faster scrolling and zooming. But before it goes prime time, Firefox Mobile just needs a friendlier interface.