I love the armory system and before I get flamed or called white knight i want to point out i played ffxi for quite along time and the running back to the moghouse to change jobs to run back to the party was very much a waste of time.
Being able to change on the fly helps a lot and yes everyone can use any job they want but most people have a job or 2 they love more then others and will play them first, like me im a DRG/WAR kinda guy i'm not a big fan of other jobs (though i got 49 blm and raise on cnj...i think O.o) so it might not be for everyone but its going to stay and i love it