I have previously downlaoded the Firefox 4 beta 10 and the biggest turn off for me is the memory issue. It eats up about 1gb memory and slow my whole system down. So, I unistalled it and turn to Chrome instead.
Now, Firefox 4 beta 12 has fixed this memory issue and now I taking it back to the testing again. With this release, I'm quite happy with the new interface and the add-on/extension page. It feels like Firefox is back to the ring again to fight with Chrome.
Nevertheless, it's still early to tell whether Firefox will win back my confidence in it but I can see the Firefox 4 beta 12 is going the right way. I also can see that the Firefox developers are really listening to the users' feedback (I submitted the memory issue feedback back then).
Finally, it's still in Beta version and no doubt there will always some bugs pop out here and there. If it's getting to annoying, I'll just submit feedback, turn to Chrome and wait patiently for the next release. :D
How to turn on "do not track" in Firefox 4?
Go to the Option screen by click on top left corner Firefox > Options > Options. Checked the option as shown below.
What happened if those website refuse to listen (to the do not track option)? :P