I don't see the issue with a game being long. If you love it, that's just more bang for your buck. People should complete the games they start instead of creating a huge backlog. I bought Person 3 Portable a few months ago and have not bought anything else until yesterday.
As for Final Fantasy XII, it's a very well made game with some aspects that you may love or hate. You do get to "choose" what enemies to face since there are no random battles, and enemies inhabiting environments you pass through can be clearly seen and avoided. The battle system relies on your ability to construct an adaptable series of tactics prior to battle -- for example, X party member heals anyone the moment their health drops under X percent. Think Dragon Age's tactics except much more useful and streamlined. It's very cool and if you play the game properly, there's a lot of satisfaction to be had watching an efficient working party take things down (I know a lot of people who disliked the combat because they tried to micromanage every battle through the menu). There's also a ridiculous amount of extra bosses for you to hunt down for powerful loot, and a lot of them are pretty challenging.
The presentation is top notch and it goes back to a more medieval type fantasy that's reminiscent of older titles. The art direction is superb, the world feels very real, and the game runs and looks great. The soundtrack is definitely one of the best out there as well.
As for the narrative, it's pretty well executed. Some people felt that the focus being taken away from the younger main character wasn't right, but no one wrote a bible on how to tell a great story. The characters are a lot of fun and the plot itself is similar to that of Star Wars, so you're in for a good time.
It's fun, well paced, adventurous and it's quite different from the types of JRPGs you apparently aren't a fan of. It's also cheap as dirt now and offers 40+ hours of gameplay.
Bad things about the game (and they aren't nearly all that bad) would possibly be the license board -- just seemed a bit sloppy and as you advanced your characters, they became less unique. And as is typical in almost every long RPG, you'll find times where the pace of combat can drag a bit.
I have not played it for a long time, but I can't remember any glaring flaws that would keep me from recommending it.