Final Fantasy XIII mini review:
Personally, I find FF13 to be the most challenging FF game to date. Square Enix pretty much eliminated the need to grind until AFTER you beat the game. There aren't any super cheap, one-shotters or anything like that, but instead the game requires you to keep a keen eye on things in battle, as well as having the correct roles placed for your characters depending on the situation.
The only things, in my opinion, that seems to be lacking in the game are the characters and story. While some of the characters are great (Sazh is awesome), the others seem to fall flat since they know more about the story than the player does, and that's a big no-no! They aren't presented that well, but the story as a whole is feasible and so are the characters and their emotions. Also, the world isn't fully realized and SE doesn't go into great detail about it, which is kind of disappointing since the world in FF13 is beautiful but lacks any sort of backstory for the player to get engulfed in. Compared to Spira and Ivalice, Cocoon/Pulse just doesn't compare.
Overall and all things considered, I'd rate the game an 8.5/10. Very, very high praise for the battle system since it's truly excellent. It's a mix of Xenogears and Final Fantasy X-2, but super fast.