I haven't tried FireFox for mobiles yet, but I have been using FireFox4 on my dektop the last few days since it came out, and I'm really liking the simplicity of it. Nice and clean. SOmething like what Chrome was supposed to be, but better, in my opinion Firefox Storms the Small Screen With New Firefox 4 for Android | Webmonkey_| Wired.com
I like Firefox 4.0 for the desktop too - and thought the same thing. It's cleaner and easier to spot the buttons for what you are wanting to do; although I did feel the overall lack of color (drab gray) was depressing me , so I added an add-in that gives color to the tabs.
I'm waiting on installing FF4 for Android until some of the bugs are worked out. When I checked the comments for the app in the Android Market, there were far too many complaints about it. I'm happy with the simple Anrdoid browser that came with the phone, so I'm not in a rush to use something else.