the thing about firefox is you have to be very selective of what extensions you install, many of them confilct and some of them are just plain badly written.
Raw firefox i've found no bugs, works smoothly for me, but with some extensions i've found memory leaks and other nastiness.
Currently i'm running:
Tab mix plus
Noscript
Mcafee site advisor
Adblock
morning coffee
With no problems, though page loading is a little slow, I don't ming living with that for the extra security.
I'm sorry, but you'll have to go a
long way to convince me to abandon FF