And they're starting to flow in.

Lightning Returns: Final Fantasy XIII for PlayStation 3 Reviews - Metacritic
Lightning Returns: Final Fantasy XIII for Xbox 360 Reviews - Metacritic

Seems like the critics are "mixed to positive", but it all depends on the critic and what you feel is good/bad.

I'm taking the reviews from users with a large pinch of salt at the moment - it's unlikely many if any of them have actually played much of the game given it's only been out for a day. It comes as no surprise to see a bunch of users instantly writing the game off with a load of 0/10's, while at the other end many people have jumped in high because they love the series. Over time, the user reviews will probably become a little more accurate in defining how this game is viewed by the people who actually play the game.