I've been playing Final Fantasy XIII the last few days and so far it has been great. I've only played through one other Final Fantasy game the entire way through at that was FFX on the PS2. I loved that game and so far XIII has brought back a lot of that familiar enjoyment. The quality is top notch and the story is pretty darn interesting, although not entirely immersive. Apparently it's normal in Japanese RPG's to start off the game with all kinds of unknown terminology and then slowly explain what the heck it all means throughout the game. This one has plenty of that.
My favorite thing about this game so far is easily the combat system. At first it's confusing and frustrating since it's done in real time. No slowly thinking about your next attack with this game. You have to act fast or you will get crushed. Once you get used to it you can swap play styles on the fly back and fourth super easy and effectively.
I did hit a wall last night with a particular boss that out of no where is all the sudden super hard compared to other encounters up to that point. I spent a good chunk of last night grinding through easy fights to build up my characters and equipment. That was a bit frustrating as I would hope the game could scale better as the gameplay goes on, but not really a huge problem. Grinding can be satisfying if it means having a bunch of new abilities at the end that you can use to slap around whatever was giving you trouble.
This early in, roughly 10 hours, I'd definitely recommend checking out this game if you haven't tried it yet. I went with the PS3 version to experience the HD cutscenes, and I already feel like it was well worth it. I do miss those achievement popping sounds, but not a big loss.