I tried "grand paradiso" or whatever the beta for FF3 is called.
I guess it was ok, I didn't notice anything all that different from 2.
Stability wise I can't say much because I didn't really use it all that long.(I haven't had good luck with beta FF releases anyway. I remember being extreamly angry with Deer Park. )
i was using gran paradiso the day it came out for a good while,but eventually i missed the foxytunes extension,and some sites with pdf werent loading up.