I think it's an outstanding game in the FPS genre, its main strengths in my opinion are as follows:
1. An engaging story set in a unique atmospheric environment;
2. An interesting character development concept (based on ADAM);
3. Good difficulty of combat, challenging, but not overly so (on medium setting);
4. A matter of taste maybe, but I really liked the nice oldies songs playing from time to time. That's something I enjoyed in Fallout 3 as well
On the minus side - I would like a menu option to disable Vita-chambers in the game to make mistakes a little more punishing. Also an instant autosave would be a nice improvement, cause you really get to use it a lot through the course of both games. Later I'll add a bit of comparison between Bioshock 1 and 2.
So, if you have played these games, chip in with your thoughts on the subject