(How does this not have a thread yet?)
I am in love with this game; it is truly beautiful. I made sure I had zero exposure to the game before it came out, I wanted to keep everything a secret so it would have a greater impact playing through it. I had very high expectations and it met virtually all of them. It's very similar to Rez at it's core, but at the same time there are many differences. It's about the exact length Rez is, but it has unlockables clearly presented that might entice more people to put more time into it. It also has a hard mode that will be interesting to try once I have gotten 100% on more of the archives.
If you liked Rez, you will like this game. If you loved Rez, you will love this game. If you hated Rez, buy this game anyway so us sane people can get a "third Rez". ;-)
One great thing about this game as you can play through it somewhat casually and relaxed, or you can play for score and have a much different experience. Last night I was playing for a high score and that after finishing the level I had to stop for the night because I was so pumped up that I though my heart might explode. I didn't really think that, but I really did have to stop because I was feeling so manic that I couldn't focus or think straight. It's a testament to this game's greatness how it can be insanely intense, or somewhat relaxed depending on how you play it.
For those enlightened individuals who are or will soon be playing this, I suggest turning off your lights and wearing headphones when you play this. I started doing this with Rez and now find it difficult to play any other way. It's also a good idea to turn off the 360's pop-up notifications to not taint the mood of the game.
Oh, and one more thing. Don't let the "Better with Kinect" branding scare you off. I don't have a Kinect and won't until they cost half of what they do now. And based on my experience with the game so far, I don't think this game was started with Kinect support in mind and it was added as an option later. It makes sense as this games is meant to be a full body synesthesia experience, I imagine it would play okay, the regular controller controls are fairly simple. That said, I like my controller and don't plan on switching to anything else.