I picked this up because it was pretty cheap and the game-play and trailers I'd seen for it seemed pretty cool and unique. However, as I played, I began to love it more and more, to the point where I would put it up there as one of my favorite games of the year. Game-play is solid and involves multiple approaches to any scenario, but brutally unforgiving, your enemies die in one or 2 hits, but so do you. This creates a great sense of tension that makes the game really rewarding, and the levels are small enough that it doesn't get frustrating. Complementing the game-play perfectly, the story and atmosphere is really well crafted and incredibly unsettling. I relate it most to the movie "Drive", but more trippy. The music, the constantly flashing lights, the twisting crazy story, and brutal nature of the game-play come together in a great, truly unique package.
other details: the game took me about 5-6 hours to beat (which seems to be the average time), after which I promptly played through it again. second play through was a lot quicker, but still really enjoyable.
There are multiple endings, to unlock the final one, you need to find a collectible item in each chapter of the game, which adds to replay value
The game's soundtrack is really cool and all the songs are just files in the game's folder, so buying the game gives you access to the OST
There are rumors floating around the internet of the possibility of a level editor, which would allow users to create and share custom maps, extending the replay-ability of the game indefinitely, and future dlc or a sequel are already in the works.