BioShock is fucking great - literally one of the best games I've *ever* played, and without question the best FPS I've ever played (even better than Marathon, so help me).
I can't believe it took me this long to figure out, considering that I'd had the game since launch (pre-ordered the bad boy). When I originally sat down to play it, I got disorientated and didn't get hooked, so after a few hours I ejected it. The only reason I didn't exchange was because of all the hype, which I now understand to be totally justified.
I suppose the issue was this: BioShock actually gets better the further you get into it - the first hour or two really doesn't do the whole game justice. This is completely contrary to most modern games, which load the first two to three hours with pretty much all the best content and set pieces (save the grand finale) to entice people (and reviewers) as quickly as possible. BioShock, on the other hand, is more like a bottle of fine (Arcadian) Merlot - it just gets better and better over time.
I still think that it would have been nice if there was more variety in the ways you interacted with the NPCs - Tennenbaum especially - but given the game's genre, what it does already is pretty darn spectacular as it is.