After getting an early copy, I can say that Bioshock is the most important game in a long time and great for gaming.
The game is not perfect, like no game can be. Some of the shooting feels less than satisfying and the enemies don't always seem to offer the most dynamic challenge. The game is somewhat easy to get through, but a challenging shooter is NOT what Bioshock is about.
This game is about taking in-game atmosphere and storytelling to a whole new level. The world is crafted so well and with such great care that it is easy to get lost in all the subtle detail never seen before in a game like this. The FPS hybrid system works well enough in Bioshock to freshen up the gameplay and the special powers you get are fun and interesting, but again it's all about unravelling the mystery of Rapture and exploring one of the most beautiful and interesting worlds the videogame industry has ever seen.
If you appreciate the little details in storytelling and world building, then Bioshock will put a huge smile on your face.
This game should serve as a wakeup call to all developers as to what it means to really tell a story and how to really present a world in a game.
I really hope this game sells as well as it is being reviewed, b/c more games taking notice from this masterpiece would make the industry much deeper and stronger in quality.
Welcome to Rapture indeed.