Finished the game and I haven't felt this way about a game in a long time... which I should preface my following thoughts by saying I don't exactly know how to feel.
What I mean by that is, Mirror of Fate is a bipolar game. Some parts are extraordinarily good; like, there were moments, more times than not, when I audibly said "Wow!" while playing through the games ~10 hour campaign. From the music to the story, to even combat and the graphics, there are parts of the game that makes this one of the best 3DS games to date. But then, on the other side of the coin, there are parts that are so extraordinarily underwhelming, that I couldn't believe I was playing the same game.
When the music isn't utterly fantastic (mostly during boss fights, or while playing during the games many set-pieces) it is subpar, blah and just uninspired. The story, while great in a man-the-lore-they're-setting-up-could-really-go-some-pretty-interesting-places, the way it's told is so far up its own ass, it makes the whole thing feel kind of hokey and just silly. The combat, again, while excellent overall sometimes feels too clunky and unresponsive, especially during moments when surrounded by multiple enemies and the art of the game, as well as the 3D effect, were fantastic and both gave life to the many locals you visit throughout the course of the game, but I personally thought the overall graphics (as in the polygons) were just plain ugly.
Mirror's of Fate is just so polarizing it's almost schizophrenic. That said, I definitely enjoyed my time with it. Don't know if I'd pay full price if I had to do it again, but I'd still easily recommend this game to anyone, especially someone who liked the original LoS more than a little bit. All I know is, I can't wait for LoS2.
Speaking of, Mirror's of Fate is to Lords of Shadows 2 as Chain of Memories was to Kindgom Hearts 2.