Here is a look at Firefox 4.0rc for Android. It looks quite good!
http://www.youtube.com/watch?v=W4O_9QLiqxs

Great usability (enahnced pinch/zoom)
Good performance (not quite opera mobile, though)
Nice features (OSS, extensions, fullscreen browsing, bookmark/password sync)

It looks as if FF4 is a solid contender for mobile browsers.