On the audio side, the whole jazz theme is unique, unsettling, and immersing. The use of audio diaries was also a great inclusion as well - I hate picking up crap I have to go into a menu and read in order to get more out of the story (Serious Sam comes to mind, although that was reading material about how to blow up headless suicide bombers). Technically, however, I've noticed that when too many sounds are playing at once, the engine will cut out certain ambient noises, as if there is a limit on simultaneous tracks being played.
Overall, Bioshock so far feels like a "best of both worlds" gaming experience - it has the seamless storytelling of Half-Life combined with the thematic punch of a Kojima game (or at least the thematic punch that he attempts at).
I'll make sure to follow up with a final judgement once I finish the game.