They have clearly jot some work to do then as it clearly didn't work, so I guess we will have to wait for the new javascript engine and not just tweaks of the existing one. Personally I don't feel firefox is that slow in browsing.
As I have said speed is only one aspect, if you can't live with the interface (Chrome & Opera, tried them a few times and really didn't like them), or a lack of configuration of add-ons, etc. then speed is irrelevant.
I have grown very comfortable with firefox, so spending time checking out other browsers for me isn't productive as I say, life's too short