I forget exactly when I played this one, but it was slightly recent. And yes, the Job System makes the game.
Frankly, it's easily borked (Mystic Knight + Hunter + Ninja + Mimic anyone?), but that's probably something that works in the game's favor. I wish more games had this kind of class flexibility - FF6 kinda came close by putting the "jobs" into the hands of the Espers, but still. Although for a multiplayer game, I'd probably handle multiclassing in D&D style - take a level of whatever class you want here and there.