The best new features include restore session for when Firefox (or Windows) crashes which allows you to reopen lost tabs when restarting Firefox. The stability of Firefox has also increased dramatically. It also includes a spellchecker which is more useful then annoying though it could use some improvements. Firefox 2.0 is a branch which means there will be no new Gecko. Firefox 3.0 is a trunk and will include Gecko 1.9 sometime in 2007.