Big Tuna,
The stable version of FF3 was released about a week ago.
I've had the beta version for almost three months now and to tell you the truth, I never experienced a problem, even with the beta. I upgraded to the official release the day it came out and I can't say one negative thing about it.
When I went from FF2 to FF3Beta, out of my twenty or so extensions only 1 (StumbleUpon Toolbar) didn't work at first... but a patch came out less than a week later. The transition was pretty seamless actually.
Just give it a try... you'll never want to see FF2 again. FF3 is leaps and bounds above it.
happy downloading my man!