I'm pretty happy with FF4. It's definitely faster.
I did have to do a couple of tweaks to get it back to what I was used to seeing in FF3, though.
I think I outlined them in the FF4 thread.
http://empegbbs.com/ubbthreads.php/topics/343658/FireFox_4_0#Post343658
_________________________
10101311 (20GB- backup empeg)
10101466 (2x60GB, Eutronix/GreenLights Blue) (Stolen!)