I played the demo ... didn't like it. The graphics are great and everything, it just the first time your character uses the Plasmids I didn't get it.
You survive a plane crash, you survive drowning, you end up in an underwater city, obviously a dangerous place and then you inject yourself with an ominous red gunk, gain electo-powers just to open a door.
In the demo I played no-one tells you to inject the plasmid, you just do. I hate that in gaming, doing things just to move the game along.
But I heard a rumour that when you complete the game (8 hours if rushed) you get 800 points, now I'm tempted to rent the game, rush it and collect those points.
BioShock, not my cup to tea, I'm afraid. I'm waiting for the new Rainbow Six game