Iv'e played for about 4 hours now, and I've got mixed feelings about it.
It's definately a fantastic game, but, so far at least, it doesn't really feal like a 'shock' game.
The levels are too linear, there doesn't seem to be many roaming enemies, I miss the hacking mini games, and having non enemy npcs who you can't interact with is quite jaring.
On the plus side, the graphics and art direction are gorgeous (playing on PC), the world is populated with lot's of interesting things, the combat is fun, the story engaging, and I like Elizabeth.
Overall, it feels like a hybrid between Bioshock and Uncharted. It's very well done, but I don't think that it's the direction I wanted the game to go in.
At this point at least, I think that SSII > Bioshock > Infinite.