I got FFXIII on Monday, and here are my thoughts on it so far (about four hours in, I think, can't be bothered to check)
Story:
I'm really liking the story so far. The characters are interesting and unique, and none of them are super-emo like Squall. The world's mythology is fascinating, and quite interesting to read, albeit a bit wordy. The datalogs are loaded with interesting stuff, but also with retelling the story that's already been seen so far, so you have to skim through it to find the good parts. Also, Vanille's accent is REALLY distracting, but other than that the voice acting is solid, and really adds to the experience.
Gameplay:
The battle system is awesome. It can be a bit easy at times, though I suspect that's because I'm not very far in the game yet. I'm really liking paradigms, especially being able to make my own, it's better than Gambits in XII, IMO. The experience crystogen system is kind of novel, but intuitive, and not distractingly complicated like the equivalent systems in X and XII were. As a whole, it works really well.
The field is a mess. I'm constantly fighting the camera, especially when I go up hills or stairs. It wants to zoom way too far in, so that your character blocks your vision, and it rotates when you don't expect it to. This problem is thankfully easy to work around, by relying on the minimap for most of your navigation, only keeping an eye on the main game screen for items (which are anywhere where there's a dead-end) and when trying to get a preemptive strike on enemies.
When people said this game is linear, they weren't kidding. There's no towns (so far), no shops, very few NPCs, and as much exploration as in a 1999 FPS. The different environments all look and feel different from each other, but as a whole the game has been an exercise in running through halls, straight streets, corridors, and narrow paths, and stopping whenever there's a battle or cutscene. I knew to expect linearity out of this game, but figured it would be in the form of a lack of sidequests or decisions. I hadn't realized that even the individual areas are completely linear. It'd be nice to be able to backtrack more than just the current area, even if there's no good reason to.
Graphics and Music:
No surprises here. It's gorgeous, just like in the trailers and gameplay videos that have been all over the internet for a while. The music is enjoyable, but I wish I could hum along with it as I could with previous games (I know, no Uematsu this time around).
Final Words:
Overall, this game seems to be relying solely on the story and battle system. It's a damn good thing these are so strong, because if either of them wasn't GREAT then it'd be easy to just stop playing and not finish the game. As it is, I'm driven to keep going. Here's hoping there's more to do after a few more hours.