No, I do not use Firefox as the Sun Java stuff crashed my system and that was far too costly an experiment.
seriously? wow, I am surprised you had a problem with that... how long ago?
the last version of 2.X was / is quite stable, and I have never lost a session or crashed with anything java related (granted I went into sun's settings and disabled a ton of stuff).
also I am pretty sure it helped that from a clean XP install after all updates I installed firefox and set it as my default browser. from there I did all flash / java add on's directly in firefox. I have heard of weirdness if you installed java (for IE) then firefox after.