Bare minimum but quick....
I downloaded FF4 on Monday. I've struggled with it until today. Gone back to latest version of 3 and all is well again.
FF4 was slow and jittery when surfing, even with all addons disabled. Lost patience with it...
Took the view that the appearance had changed that much I may as well try the others. Flirted briefly with Opera, Iron, and Safari. Gave up and came back to something that works.......The addons make it for me. Hopefully 4 will be fixed for my machine by the time it's launched....But I won't change until my favourite addons are updated....
I've never had any problems with FF in the past!!