Although the previous entries in the Final Fantasy series have had excellent soundtracks and relatively vivid and impressive settings, I think that FFXII was the most absorbing of all the worlds that Square-Enix have created.
It feels very much more of a complete package. Although X had 3-D environments to explore the game itself was really linear and you were hand-lead through one locale to the next. Visually impressive at times (Macalania Forest is utterly beautiful), but it didn't instil me with a sense of adventure I had. People often compare XII to an MMORPG and I think it's a valid comparison even outside the gameplay. The ability to explore the huge world with monsters roaming about, with an impressive soundtrack and the ability to see your characters explore them really allowed me to be immersed in the game.
Some of the locations (Sochen Cave Palace and the Salikawood spring to mind) are not only visually impressive to see, but the music compliments them perfectly. Sochen Cave Palace felt epic, undiscovered and forgotten and the music really conveyed this emotion. The Barheim Passage really gave the impression not only that the place was grimy and underground (in every sense of the word), but that something would appear from round a corner or you'd get blown up by a trap. Which brings me to another feature: the traps. As irritating as they were, I thought it was another element that would sometimes force you to be on your toes and be prepared for the unexpected to happen which I suppose happens in adventuring.
So between the added features (traps, monsters), being able to roam freely around a huge world, a very atmospheric and immersing soundtrack and the general size and scope of Ivalice, I found FFXII to be the most immersing and impressive game in the series so far. What about you? Were you impressed by the changes from the other games in the series? Or did you find them irritating and unnecessary?