I'm impressed by the game too. I downloaded the demo a bit over a week ago, and was impressed enough I bought the game the next day. The fantastic music and atmosphere hit me first, then the free-form singing mechanic hooked me (for some reason, I love being able to make my own music in games). The game continued to amaze me with all the little bits of story that hit just the right note; Naija's wonder at the world around her, the way the game slows down the first time you break through the Veil, the saddened narration that comes when you defeat a boss, and the ending and hidden ending, which I adored. These moments managed to convey the right feelings without explicitly explaining anything to me, which fits perfectly with the idea of exploring a wondrous world at your leisure. You don't need the details, just the theme ideas presented, which the player can then react to on his or her own.
Naija's narration was particularly effective, both artistically as well as in terms of gameplay; the simple fact that she was commenting on the world suddenly becoming dark, or that she had spent so much time killing things, made me accept shifts in gameplay and narrative a lot more.
I finished it today, and then I came here to see what other people were saying about the game. It's a little bit funny seeing the reactions people had a year ago, and then comparing it to the patched version of the game that I played. It seems that most of the issues people had were resolved in the patch, which is great. The map in the main game is a lot more usable than the map in the demo, for example, and the widescreen support is nice.
The only complaints I have are that the game could stand to point you in the right direction a bit more in the early part of the game, and it can be a bit shootery at times, especially early when you don't have all your abilities. A few more save points and giant turtles would've been nice too; it's not a problem later on, but early in the game it can be mildly annoying. Still, the game is so impressive these things were easy for me to forgive. I love the world you created, and the way the game let me explore it and fill in the blanks myself, without overly imposing its own interpretations or beliefs upon me.